There are some packs of Christmas hamster treats in p@h. They are shaped like Christmas stocking, stars etc. You could get those and make an advent calendar or buy an advent calendar that has little pockets or boxes to put the treats inside.
http://www.petsathome.com/shop/Produ...storeId=10151#
There are other Christmas treats and small animal stockings available. As well as other Christmas chew toys, tubes and a house.