Non-Canon Compatible Flash Unit - G3?

[numskull]

sorry for repeating myself, but I posted in the "Flash" section with no luck!

Just got a G3 last weekend - (great so far!). I've been looking for any information / advise on the web regarding the availability of non-Canon flash units, but can't seem to find any answers. Anyone know if units from Vivitar, Sigma, Metz, Cobra etc are definately compatable with the G3 on auto mode - ie, they'll do the same as the Canon dedicated Speedlite units.

Any help appreciated.

Num