I bought this bottle opener at a fancy mens shop in Austin, so I probably overpaid. It war around $12. I'm sure something less expensive could be found, but it does seem hard to find any that are nice metal, have a nice shape, and don't have a beer brand name on them.
I drilled small holes and used a rivet gun to slap it in. I hope it won't leak, hopefully the expansion of the rivets will make an ok seal. If it does leak, well, at least I can open a beer to help forget about it.
I really like the look on the bike, and have received several compliments. My only regret is possibly not putting it higher so that it could be used if the case were on the ground too, but I still like it this way.