In no particular order:
- Kijiji - the odd used door, refinishing is an easy task.
- eBay - you might get lucky and find one on our side of the border
- KLOV - used or new.
- here - same deal.
Honestly shipping on a small one like that isn't that bad. I just paid $10USD to a guy in KLOV for shipping on a new door similar to that. And the door only cost me $35USD.
GRANTED, buying a brand new 4 player door with the over under, brand new, from a vendor in the states (which shal remain nameless) cost me about $350 Canadian all said and done. Plus two months of a nightmare deal trying to get another lock for it from him when I wasn't sent the right keys....
Shipping is sorta something that comes with the territory for some things I'm afraid. You might find your cheapest option is to buy a used door locally, strip it, then refinish it.