Ideally, I'd look for the Canon EX series flash unit that also has a non-TTL flash sensor on it. Which means that you may want to hunt down a 580EX or 580EX Mark II flash. Use that with a hot shoe adapter on whatever old camera you have. That way, you don't have to tape the bottom of the flash foot to prevent shortcircuiting to the cold shoe on a Spottie or whatever other old camera you're using.

Use your 430EX as a slave unit or as a compact unit for when you're only taking the Canon bodies with you. Or, as trade fodder for the 580.