I did see a canopy once in the field, I believe it was an Arty carrier (M113) and the driver had a Plexiglas canopy that clamped down over the hatch. We were all gob-smacked when we saw it! Didn't get any pics nor have I seen one since but I swear it was real.... Sort of a helicopter bubble with a flat windshield at the front complete with windshield wiper.. We were all bundled up (I was driving my TOW carrier) and the guy driving the canopy carrier wasn't even wearing a jacket, just his regular combats, beret and head set... under glass of course.. ;-)
That well could have been me back in the day here in Shilo. We used to do this with the M113s when I was with 2VP in Winnipeg as well. The bubble was actually the cover for the M577 ARV. As mechanics, we would order it on the work order, then adapt it with a piece of plywood to fit onto the hatch ring of the carrier. The windshield had a defroster and as well we either adapted Iltis wipers, or used the original US type wiper motor that came with them. Some of the guys would go a bit further and install a sun visor as well.
While the bubble helped a lot, just as important was to block the engine from drawing it's air form the crew compartment. No heater was going to pump out as much air as a 6V53 would draw. There was a small vent located by the driver's right leg. You had to pull out a cable to partially block it, then insert a chip bag or something to totally block it.
The bubbles were over 1K each, not including the accessories. They were also easily broken. Unfortunately there were never enough that they would make it out for everyone.
As a mechanic, I would often pull up to a M113 casualty where they were in full AFV winter gear with balaclavas and icicles hanging down from the eyelashes and mustache. I almost felt guilty being in the beret and combat shirt.
Officially, the M113s were issued with windscreens designed and built by 202 workshop. They could be described as marginal at best.