Yeah, the guy I bought the hand grip heaters from (on ebay) actually emailed me saying there would be a delay because of stock.
The hot water freezing faster thing is when you wash cold windows outside, with hot water. It evaporates very quickly, thus leaving a very thin film that quickly freezes. But adding hot water to your tank will serve to bring up the temperature somewhat, as well as mix things up a bit, seeing as the warmer water will naturally migrate to the top of the tank.
Reflective insulating is very effective. I once owned a late 50's to early 60's house that had no insulation in the walls; only a thin film of aluminum on the back of the plaster board (a precursor to drywall). It worked quite well, as my heating and cooling bills were not far out of line with many newer homes with fiberglass insul. So combining both reflective and air-trapping insulation works very well. I used "fibrex" (rock wool) and a reflectix type of insul in the walls and ceiling of my camper; and reflextix type on the floor, to help limit heat from the exhaust pipe, in summer.