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)