for a few days, water and apples will be fine, give him some large portions.
you could get him cut up pear, buy a bag of frozen peas, and green beans, give him some in a bowl at night time 9pm. a treat of honey on spoon. and if you can you could get some dried mealworms from walmart bird section I buy Kaytee brand.
put 4 or so worms in with peas.
he'll be fine in a small cage for awhile.
gliders can run away easy if not bonded and not kept properly. and you are right the cold would be very bad for him very fast.
if you dont want him, you can list him here, or other glider websites, or craigslist.