This would be as good a time as any to start doing some research and reading, and get a hand in, and do it yourself.
I know that we have discussed several different methods of converting the Small Frame Martini's, here in the past. There are a couple different ways to go about the job, ranging from simply lowering the ears on the lever, which lowers the breech block and realigns the existing firing pin to the center of the bore, all the way to installing a new face on the breech block and making a new firing pin. Some folks also simply grind the breech face back into alignment with the barrel. Belt sander!
I have read, but not been able to confirm, that BSA themselves, did not change the breech block face when they made rimfire vs centerfire guns.
There are a lot of things out there that you can pound money in to, and as long as you understand that it won't be cheap, and it won't ever come back to you in resale value, if it makes you happy, go for it. Good luck in the search, if you don't dig in to it yourself.
I have a action that has been converted by grinding off the ears of the lever. My ambitions for it are to make a Hornet based gun, either a .22 or .17. Project number....???
I would also suggest checking in on the ASSRA forum, as well as the Saubier Small Caliber forum, for suggestions. Be sure to mention that you are looking for a Canadian 'Smith. You may get some results there.
Cheers
Trev