Sleeping Rolls of Warmth

Mages don't travel often.  They have too many tomes and research that can't be carried around easily and they'd rather be researching then riding.  But for those mages who have to travel or just want to want to travel want to be comfortable.  One of those was the royal mage Sentorian.  He had to travel with the High King often, but was always cold in his sleeping rolls, no matter how many blankets he added.  Thus, after returning from one long adventure with his High King, he created a sleeping roll of warmth.  The roll emanates low amounts of magic aura, but works wonderfully.  It keeps the sleeper at a constant temperature, determined by the user.  It works for about 10 hours then has to recharge itself for at least 10 hours before it can be used again for anything other then a normal sleeping roll.  They used to be very common, but people aren't as interested in paying so much money for a sleeping roll, so they are harder to find.