I have found great results from a farm and Ranch type hardware store here in Vegas, with the o rings sold there. If you are fortunate to have a store such as this near by they have lots of different diameters and thicknesses. I matched up the FMF ones and bingo! .35 cents a piece. Those along with your favorite RTV and you are golden.
I am curious as to the longest any of us riders have gotten a set to last?