A spell prerequisite may be provided by a character who has prepared the spell (or who knows the spell, in the case of a sorcerer or bard), or through the use of a spell completion or spell trigger magic item or a spell-like ability that produces the desired spell effect.
If I have a Wizard with Scribe Scroll who is able to cast a spell not on the Wizard's spell list as a Spell-like Ability, would he be able to scribe a scroll of that spell?
As you've identified, Spell-Like Abilities are close enough to spells to supply a spell for Crafting purposes. You meet the requisites for Scribe Scroll of "knowing the spell" insofar as the game system cares due to your linked quote.
To pull more information from where you linked:
Some individual items, notably those that just store spells, don’t get full-blown descriptions. Reference the spell’s description for details, modified by the form of the item (potion, scroll, wand, and so on). assume that the spell is cast at the minimum level required to cast it.
This line establishes that the rules presented do apply to potions, scrolls, etc.
Construction: With the exception of artifacts, most magic items can be built by a spellcaster with the appropriate feats and prerequisites. This section describes those prerequisites.
This establishes that the Requirements section (to follow) are crafting "prerequisites", effectively equating the two terms.
Requirements: Certain requirements must be met in order for a character to create a magic item. These include feats, spells, and miscellaneous requirements such as level, alignment, and race or kind. The prerequisites for creation of an item are given immediately following the item’s caster level.
A spell prerequisite may be provided by a character who has prepared the spell (or who knows the spell, in the case of a sorcerer or bard), or through the use of a spell completion or spell trigger magic item or a spell-like ability that produces the desired spell effect. For each day that passes in the creation process, the creator must expend one spell completion item or one charge from a spell trigger item if either of those objects is used to supply a prerequisite.
And finally, as you noted, SLA count as casting the spell.
