Searching instances of 'expend' (as Spheres of Power (SoP) uses the word expenditure for anything relating to its points) and 'Spell Points', I don't see any Magic Items that do what you're asking. Moreover, some of the context/flavor in SoP suggests that it was designed to avoid such items.
He wants to create a powerful scroll – a trump card in case he’s ever out of spell points
Some related things that may help:
An old standby of magisters, SoP has streamlined item creation and generally made it easier to duplicate your spells instead of increasing your slots. Some custom Wondrous Items fall into this area as well, but don't allow for more (flexible) points and require you to select your Sphere at creation.
SoP Permanents: Rods, Wondrous Items, Staves
Rods and Wondrous Items are essentially the same in SoP, except that Rods are at-will whereas Wondrous Items are typically 1-3x/day or at-will with 50 charges. Either way, you are able to select Talents that you no longer have to prepare. Staves don't really help you except that one option for staves is permanently providing a Talent.
All that being said, SoP repeatedly states:
Magic items are at their best when they are unique, wondrous, and personalized, which can mean creating new abilities beyond the scope of the basic spheres. The GM is the final arbiter for determining an item’s final market price, and may adjust a price higher, lower, or even disallow any item or option if it becomes unbalancing or disruptive.
If your GM is OK with it, you can totally make Pearls of Power that apply to Spell Points instead of Spell Levels.