Questar is one company that does cross border stuff like that. CZ-USA will not sell to canadians as there is an established CZ distributor, not even magazine parts. If you do find a way to order a custom shop SP01, and you are thinking of using it in IPSC competition, make sure they understand that it must conform to IPSC world rules.
It might be easier to buy a stock one up here and using a form 6 to get it in and out of the states, have it worked on by their custom shop. But you can get as good work done here in Canada.
The items legal for IPSC are fairly simple, any competent gunsmith could do them, one familiar with CZ's will likely be faster and cheaper.