Percussion kits its in Canada are not available period unless you order one through a broker from the US all in very pricey.
The value of the traditional rifles have dropped considerably in the last few years, there are lots of safe queens available I bought a TC White mountain carbine in excellent shape for $300.
Supplies for 54 cal. are dying out fast, go with a 50 although most available bullets are geared towards inlines a round or a Minnie ball mold solves that.
Casting bullets I find relaxing camp stove, cast iron pan, mold and a spoon Bob's your uncle
In Canada supplies are thin a few suppliers scattered around shipping starts at $20 no one shop has everything, Track of the wolf has everything shipping start's at $40 US for anything even a nipple,
Most of the accessories required can be made yourself ball starters, powder horn, possibles bag etc. great for these long winters.
Shooting a caplock is more affordable these days than centerfire if you can find the supplies
Buying a used in good shape caplock and restocking it would be a good project option getting a blank imported is an option, always check the bore for rust and pitting a bore light would be an asset.