Here it is. Inside dimensions: 1000mm L 500 W 450 D. Big enough to hold 2.5 possibly 3 slabs of beer
Made 2 boxes, one 3.5" smaller than the other in all dimensions. Glued that white packing foam (1.75" thick) on all surfaces of the smaller box, Slipped the bigger one over the top. Even just to keep the OTA in it & leave it in a cool room all the time would have to help. I'd rather see it kept at ambient though somehow.
A normal bought esky would do just as well. Why not just cut a hole in the esky & mount a fan & peltier system to that? Have the scope sealed, naturally. If you could preset the temp to whatever you wanted, roughly to what your ambient gets down to normally in your area (here its about 6-8C this time of year) You could have it running 24/7 if you wanted to at home.
Food for thought.