The RPod 150 fits our Compact perfectly, even with the wings. It should also fit an Airflyte sized trailer without wings. We found one online. For just $109. It has already held up through some pretty nasty rain and wind. We're keeping our fingers crossed.
Interesting, yesterday the wife saw a listing on ebay for a specifically stated Shasta compact cover with zipper door entry. No idea of the quality, but it sure does demonstrate the increased spotlight of these campers last few years.
I would strongly, strongly recommend against the use of a cover. In collector car circles the topic comes up periodically, and I've seen the results firsthand on too many occassions. There are multiple problems caused by covers, and they're far more serious than problems caused by exposure.
First off, most people buy covers they think are going to keep their vehicle dry. These are the cheapest covers on the market, but they also do the most damage. Since they can't breathe, they trap moisture (either moisture constantly rising above dirt/gravel, evaporation from the hard slab underneath, condensation, atmospheric, etc.- it's always there) against the paint and, while in the sun, cook it at high temperatures. The result is paint adhesion failure, and can happen as quickly as a year or two. It looks much like fisheye, and repair means taking the vehicle back to bare metal. Breathable covers are available, usually made of non-woven fabric (Kimberly Clark is the most common manufacturer) but they are many, many times more expensive, and because they do let water through, are rarely chosen.
Secondly, all covers, even the $$$ breathable ones, will cause abrasion to the vehicle surface as they move in the breeze. It may not sound like much, but even if the vehicle is operating-room clean (it won't be) that cover will grind against it like sandpaper 24 hours a day. Paint will be sanded off, polished metal will be fogged, etc., etc. The results aren't pretty. It's easy to spot a vehicle that's been stored for any period of time with a cover. It happened to me more than once before I got the clue.
The only proper use for a vehicle cover is to keep dust off while parked inside a garage, and flannel is the best choice for that.
You'd be far better off putting your money towards a cheap Harbor-Freight style temporary carport than any kind of cover.
I would never, ever leave a propane lantern burning unattended. A 100w incandescent bulb will put out a surprising amount of heat in an enclosed space like that. You don't need to make it comfortable, just keep it above freezing. Make certain that all of your fluids are drained (including any drain traps) and you're probably fine anyway, but if you're really concerned than a 100w bulb or two will probably do the job. If you're still concerned you could run a small electric space heater, but that's almost certainly overkill.