As far as I know the canadian GP seat covers are not yet reproduced so I had mine made from scratch by SMS in the states. In hindsight my regular upholstery go to guy could have done it too and probably quicker. As for the outside weatherstrips (glass sweeps) I think the american Gran Prix has the same roof style so they should be available, try Ames.
the US / GP and Grand Parisienne both use the same belt moldings. The original manufacturer was 'REPOPS", and "PUI" now offer them also. Initially they were only
available as 8 pc sets. The may now offer the outers only ? You can Google either company. Just remember to order the GP applications
A few years back I had mine custom made from scratch by a local guy here who does real nice work. It wasn't cheap, over $2000 for the front and back seats but I sure loved the end result.
And for the belt weatherstrips I bought them from NOS Reroductions back when they were still selling them. I was very happy overall with them, just minor tweaking to make them fit.
__________________
1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles
1966 Grande Parisienne, 396 1 of 23 factory air cars