Which engine? The engines (2.5L & 3.0L) used in the P-bodies was used across a number of different models over a long span of years. Not sure about Canada, but here in the US, many boneyards can do a nationwide search. Unfortunately, the used auto yards tend to scrap vehicles 15 years or older (only keep newer models for parts inventory) so even here engine/transmission/body parts are getting hard to find for mid-90's and older vehicles. Sometimes you can luck into a yard that has the older stuff, but not often.
Is it possible to rebuild the current engine? May be your only choice.
Is it possible to rebuild the current engine? May be your only choice.