Most likely you do not need to do anything
In-combat healing is rarely an effective use of resources, usually it is better to focus on hurting the enemy. In most encounters no PC goes down, and the higher your level the most likely it is that a character is "taken out" not because of lack of HP, but by being stunned, paralyzed or dominated.
So if the GM compensates for the 1/5 decrease of party power by weakening the enemy similarly (as he should), you will find most encounters no more challenging than before.
What you can do
Skills and skill feats
Hopefully someone already has Medicine at expert level, with Assurance, Continual Recovery and Ward Medic. These provide much cheaper out-of-combat healing than spell slots.
Of course if that someone was the Cleric, someone else needs to retrain into these.
If you want to use Medicine in combat, you can also take Battle Medicine.
Natural Medicine might look tempting if you have a high proficiency in Nature, but as shown above, you need skill feats to be effective, and for those you actually need Medicine at least on expert.
These cost money, and are even less action efficient than spells.
A Moderate Elixir of Life costs 150 gp (9.4% of the total expected wealth of a 9th level character), takes 2 actions to use (1 to retrieve, 1 to drink) and heals 5d6+12, which is barely more than the expected damage output of a 9th level monster in a round.
With the same 2 actions, the Wizard could cast a 5th level Fireball, or the others could attack twice, potentially reducing the enemy damage output (by killing the enemy).
You could buy less expensive potions, but than the effect per action decreases further.
For the same price you can buy a 5th level Heal scroll, that heals a respectable 5d8+40, but
only the Champion can you need a multiclass to cast it, and takes the entire turn (1 action to retrieve, 2 to cast)
The Pearly White Spindle (Aeon Stone) is uncommon, but can provide 1440 HP healing during the day. More importantly, it heals you during the 10 minutes you Treat Wounds (or is done to you), and it tops you off during the looting if only a few HP are missing.
Many people like the Healer's Gloves, I never understood why. 2d6+7 HP is not much for 80 gp, and the +1 for Medicine checks is meaningless for Treat Wound if you use Assurance, which you should. It can be useful if you cannot use Assurance1, like treating bleed damage, but that is rare.
Its best use is on characters not investing in Medicine, so they can bring up one fallen PC once per day.
Blessed One gives anyone Lay on Hands, which is nice, but you already have one character with it. Better if you want to heal a lot to one character.
Medic gives bonuses the HP regained via Treat Wounds and Battle Medicine, and more frequent usage of the latter. Better if you want to heal some to more characters.
On level 9 Humans can take the Multitalented feat which gives you a multiclass dedication feat:
Any divine or primal caster can use Heal scrolls (which provide the most HP/gp) with just the Dedication. With Basic Spellcasting you get your own slots, but they are too little too late when it comes to healing.
Pychic provides another Focus Point which the Champion can use to fuel Lay on Hands.
More Focus Points to use for Lay on Hands
The Champion can take the above mentioned Psychic dedication, but beside that there are other feats like Litany Agains Wrath that increase your Focus Point pool. Desperate Prayer lets you use it once more.
"One ounce of prevention is worth a pound of cure".
It is much better if you do not need your healing in the first place. Increase your hit chance (weapon potency runes), your damage per hit (striking and elemental runes), your AC (armor potency runes) and your saves (resilient runes).
A Ring of Resistance (fire) is easily affordable on level 9. A Greater Grim Sandglass costs more, and negative is less common than fire, but I still found it a good investment.
Of course it is not only about damage dealt, received and prevented, as control, buffing and debuffing is equally important.
- Invest in Intimidation, a Frightened enemy is less likely to hit, and more likely to be hit
- Diplomacy + Evangelize will force a flat check on enemy spellcasters if they want to cast spells
- Use flanking and combat maneuvers to your advantage
- technically you could, you would just mostly fail against the DC of level-appropriate enemies
I mostly play PFS, for this reason I cannot know beforehand what classes and builds I will be playing along. My characters need to be self reliant.
So most of my characters have Assurance (Medicine) and Continual Recovery by level 5.
Battle Medicine can reliably heal 2d8+10 by level 6 (Assurance + Expert), which is just 1d8 less than a Healing Potion of the same level, but is rarely used, as the actions are better spent elsewhere.
There are lots of characters with the Heal spell other than Clerics; primal and divine Sorcerers, Summoners and Witches, Oracles etc. Still, I mostly see only Clerics with Healing Font using it, as they cannot spend those slots on something more useful anyway.
I played most games (in PFS) without Clerics, many without anyone with Heal, and some without any kind of healing. There was no correlation between the amount of available healing and difficulty.