If you have feral cats that live outside and just can't be brought indoors for the winter, then consider getting an outdoor heated cat bed. (cattime.com)
Products such as heated cat beds for warmth, litter boxes that accommodate mobility problems, and other items such as cat stairs or ramps to get around or get on the bed can help. (cat-lovers-only.com)
Pet World has a nice selection of cat beds, including heated cat beds, catnip pads, hideaways, wicker cat beds, fleece furniture throws, fancy cat beds, and more. (petworldnatick.com)