Depends on your budget, I am more familiar with U.S. pricing and availability so keep that in mind.
Fantasea and Ikelite make “clear” polycarbonate housings for the 350D and are probably the least expesnive options.
Fantasea’s is $999 and includes flood insurance and a port (though I do not know if the port works with the 60mm, you probably need another one.)
Ikelite’s is a bit more expensive, about $1250 where I looked, and you would also need a port for the lens.
Moving on would be the Sea & Sea housing for a bit more money, but they are dropping in price and can be had for about $1,400. Sea & Sea I think I read somewhere that someone was able to modify their XT housing to an XTi housing, and I think (not 100% sure) it may have been the Sea & Sea housing
The strobes should work with a synch cord, on the Fantasea and Sea & Sea a standard connection should wortk and on the Iklelite you can get a Nikonos connection to a Iklelite connection.
Something else to think about is Aquatica does not have one for the 350, but is coming with one in December for the 400. It is the same concept as the one for the Nikon 40DX, smaller and light than their other housings and the Nikon D40X housing lists for $1645, so perhaps the 400 housing will be in that price range [port and gear extra]. I recently purchased an Aquatica and love it.
Sea Tool also has one for the XTi/400, smaller and more money (about $2300 or so)
One thing to think about is that the cost of the housing and ports are pricey compared to the camera and the new(er) XTi/400 Rebel can be had relatively inexpensively in the grand scheme of things. (Though the 350/XT is fine.) If you go the 350/XT route, keep an eye on the bodies, they are starting to drop more. I have seen the 350/XT bodies at $450 right now (XTi/400 bodies about $600). So you may want to get a back up body just in case before the cameras are difficult/not possible to replace.
