[Utah-astronomy] Seeking O-ring for finder / Need memory?

Could someone point me to a good local source of O-rings? I need one for my finder scope. No luck at Home Depot. Specifically I need something with an outside diameter of 50mm and an inside diameter of 43mm. Also, I recently had the memory in my iMac increased and now I find myself with two 2GB sticks left over. Any interest? Cheers, patrick