or rack or whatever the term is!

My bike is built around a 1983 Schwinn Voyageur steel frame. It only has the one bottle cage, attached with eyelets or braze-ons or whatever you call THOSE things (can you tell I'm new, here? ). I would like to add an additional bottle holder, but don't know the best way to do that. I could maybe find a frame builder that would be willing to drill the frame, but would that weaken it?? I'm planning to do a very long distance tour and need all the bike strength I can obtain. I could also get one of those kits that uses a triton-class zip tie to hold a nut fixture in place and do it that way. Do those last? How aggravating would something like that be? I'll get plenty of aggravation from traffic, I expect, and don't need any extra, if I can avoid it

So, what's the current wisdom?

Thanks in advance!