I got mine in my local classifieds. I regularly saw some up for sale
, but I was looking for a specific size that would fit the trailer, long and narrow, like about up to 38" wide but no more than about 14" high . Then one day I found one that's 36X11, perfect fit, from some guy selling parts of an old motorhome he was dismantling. Got the door and frame assembly for $25.
I haven't installed it yet (too busy right now to work on the trailer).
I also checked with my local RV dealership. They could only get replacement hatches for existing RVs. They needed first the RV model and year, then they could lookup their catalog and order the hatch for that RV. They can't just simply order a standard 36X11 RV hatch like that. Too simple...
If you can order directly from a manufacturer or distributor, at a fair price, that's great. I couldn't find a good deal on my side of the border.