Okay, I know the OP is about the old school bottle dynamos, and it immediately turned into a "vs dynohub" thread as expected. But there's also this:

VELOGICAL RIM-DYNAMO - Standard Bicycle Dynamo - Smooth Running, Lightweight, Efficient

New school high efficiency sidewall-powered bottle dynamo. More expensive than the old school to be sure, but still probably cheaper than lacing up a new wheel for most people, and arguably simpler

That said, I have dyno hubs available for all my bikes and there are still days where I grab a non-dyno front wheel and have a battery pack squirreled away if I think I'll need it. If cost is really an issue, battery bank is really where the bang for the buck is.