I'm not a Canon guy but you might try posting this in the Canon Forum on this site and see if they can help.

I think their current top-of-the-line is the 580EX but it's probably closer to $400. For less than $100, there won't be a lot of options. With Nikon, some of the older high-end flashes sell for close to that (SB-28, etc) but they're not very compatible with Nikon's digital SLR's.