installing lights in shower stall
In the US you can put an enclosed, wet location rated, flush mounted fixture in a shower stall.
IMO I would NOT in that stall. Too small.
Find a way to install a recessed in the ceiling.
As far as the feed, I'll defer that to a Canadian code person. In the US there are only certain times you can feed off the bath receptacle circuit.
Sometimes I feel like if I answer any more questions it is like someone trying to climb over a fence to jump off a bridge and me giving them a boost.