I usually look at Wal-Mart, HD, or Lowes for those kind of things. They are usually cheaper than the local hardware store.
Most, if not all have a "tip over switch" that turns them off if they get knocked over. I usually leave mine on the carpet, which is relatively safe with the units I have, have not noticed the carpet in front getting hot at all, just a little warm. I never run any type of heater in the Airstream, if it is going to be unattended for more than 15 minutes.
2003 GMC 2500HD 4X4 D/A Ext. Cab
Propane Powered Honda EU2000i
Lots of Hot Sauce!
Air # 283