Are there any manufacurers who will custom build a power adaptor that works for multiple brands and devices? For traveling I would love to just bring one adaptor that has multiple power adaptor outputs rather than bringing each of the seperate adaptors for my Sony video camera, my Canon still camera, my powerbook, and my ipod. Does this sound possible?

I don't think there is a device on the market like that. However,
for powering on set almost everybody is using some form of
bauer batteries and equipment and they can interface to a host
of other equipment. Whether it will be to everything you want,
I don't know. If you know someone with an electronics background
you may have them make some custom adaptors and such.