I have a steam beer that I want to enjoy, but I realized the out post on the keg was missing the o-ring. I ran down to my local Ace and they had the 111 o-ring. Pint poured.
The 109 and 111 should be available locally. The 417 (lid ring) on the other hand could be a little harder to find.
Great that you were able to locate one and fix things.