Petco, Wal-mart, Lowe's, Menards, virtually any home improvement store. There is always ordering on-line. Funny Petsmart sells the bulbs, but not housing for it.
Just remember, no plastic cover between the lamp and the chameleon... if you leave the cover on the lamp is useless, UVB does not transmit through plastic or glass.
Not sure what part of Ontario you are at, also, please specify the size. If its the 48", some home depots have a very cheap light fixture (around $18) it actually says on the box "for 12T..." this is the one you need. I know home depot at Hwy & and Woodbine has them (that's Markham, ON)