I'm in the same habit with spare parts.
You could make up your list, and call Ruger CS. Prescott makes the SR-22. 1-928-778-6555.
The parts lists in the manual are often not accurate as to what they'll sell you (no "factory fit" parts).
My last parts order was for my LCRs. The LCR manual only lists three, IIRC, factory only parts, but they said "no" to several other parts I would have liked.