Small bolt pattern wheel options?

Alright, this is off topic but applies.
Went to O'reilly's for a "O" ring. I swear the chain stores only hire 20 year old girls(not that there is anything wrong with that) So I say,"Do you carry O rings ?" What's it for she replies."Well it's for the water pump in my motorhome".What make and year ? "Ah, not you don't understand,it's for the water,water pump". It's 2 1/2'' round and 1/16 thick, here it is, can you match it ? Computer says we have hundreds of sizes. Well do they list the sizes ? You all know where this is going !!!!!!
Sorry. But I had to tell somebody.