This is a very large and broad question - most people who would be able to answer this would only have single country specific knowledge, or would have to spend a considerable amount of time googling.
I suggest you start with the 'CFIA- canadian food inspection agency' and google 'CITES 1' 'CITES 2' they have ALOT of documentation... It took me quite some time to figure out about bromeliads, which, is very easy to get across the border (from continental USA).
Try coldcalling places that do phytos, I had great success doing that. They typically have a good understanding of what they are doing, but, this is their business, Id also double check what they say online.
Goodluck! And make sure its worth it... phytos are atleast $60, pls shipping etc, etc.
If you can wait, there are some really great members here who organize 'group buys' they do most/ALL the work, and you just need to pay a bit (i mean a bit, when the expensive stuff is shared across many people it really doesnt hurt the wallet)
Well I was thinking of ordering from Seeds Carnivores and More. They don't have a website but they do have a PDF list and a huge selection of listed plants and seeds so maybe people would be interested in a group order with them?
Stay away from importing plants and even seed of those on App.I (N.rajah, khasiana, S.oreophila, alabamaensis, jonesii).
Those on App.II (like Dionaea) can sometimes be imported just with a phyto certifying that those plants have been artificially propagated. But sometimes the customs can ask for the expensive CITES documents. Better check with your customs before you order!
You should also check national law. A lot of other CPs are locally protected. They must not be wild collected. Propagated e.g. in-vitro plants are usually ok.
First check if the seller is trustworthy. Talk to them about international shipping.
I know Carnivores and More have a lot of experience sending plants internationally and the size and quality is good. They grow most plants from seed and by division.