I like the microwaveable Hotties (I buy from Amazon - go in via Easyfundraising with Busters Memorial Fund for Cats as the chosen charity - which is Purrs based - and get a % of everything you spend donated to Buster's fund with no cost to you at all).
They are pretty bullet-proof so long as you don't overheat them. They feel warm for longer than a traditional hot water bottle and there's no chance of leakage, either.
My lot fight for space on them.
Any unwanted items you have at the end of the year (doesn't have to be cat related but it helps if you can catify the reason for including it in the Auction) can always go into the Purrs Auction - this is a bit like e-bay except all the proceeds go to the Purrs-supported Rescue chosen each year, so you may end up paying out postage to get rid of your stuff, but you could also raise tons for the needy kitties as bidding gets a bit silly when we all get a bit, erhem, excited
Keep your eyes peeled, it'll be here around October/November time so all purchases are posted in time for Xmas.