I assume that you are wanting to put together a legal semi auto Sten clone.
Dewats seem to be listed for $300 - $450, there is a Mk. III dewat in the EE right now for somewhat more than that.
I would suggest that the value of usable parts that you could salvage from a dewat would be somewhat less than the cost of the dewat. Keep in mind that you cannot recycle the magazine housing. The barrel block will be ruined, the trigger mechanism may be welded, no barrel or bolt. Stock might be OK, the trigger housing and head collar might be reusable, depending on what was done to the gun to prevent disassembly. The usable parts are not going to be worth the $300 plus that the dewat will cost.
A Cdn. sourced demil - not a dewat - is a better starting point.
You mentionned the SAS kit. There are two manufacturers of these, neither welcomes Cdn. business.
Getting a parts kit out of the US is not really an option. Export controls apply to the export of machinegun parts.