Stumbled on this website. I haven't compared prices rigorously, but just eyeballing various solid chunks & off-cuts looks reasonable from what I recall of other vendors (plastic is friggen expensive everywhere). The nice aspect appears to be CDN source. The bummer is, no information on shipping. I tried populating the cart & doing a faux checkout, but it failed to launch. Might have to ring them during bus hours. Guessing it cant be all hat bad if CanPost. At least its not USD & border fees. Anybody used them?
https://www.plastiblocks.com/shop-cad
https://www.plastiblocks.com/shop-cad