We live in Trenton and have had our '76 Trillium for three summers now. The last I talked to Tom at Trillium Parts, it seems the new company that took over from him is no longer building new Trils. And parts for the new ones like windows
don't fit the old in any case, at least without considerable modification. So in many cases the choice is to refurbish the old or retrofit.
If you look around on this website you should find some leads on used parts. Look oneline - there are places that scrap old trailers and recycle the parts like windows. If you find one in Ontario I'd love to hear. Driving around I've seen a few very weathered Trilliums sitting in fence corners. One of these days I will stop to see if some salvage is possible. Here are a couple of links:
Trillium Parts now it seems called, Vintage parts
: Vintage Trailer Supply - parts and supplies for vintage travel trailers and campers!