cubastreet
Espresso Fiend
Lots of different adaptors on thingiverse too if you have a 3D printer. E.g.
www.thingiverse.com
Yet Another AA to C Battery Adapter by enif
This simple project provides an battery adapter that allows using AA size cells in appliances made for C size cells. The construction consists of two thin cylinder which are not entirely close but joined by two tight turns which form a small gap. The construction is inherently flexible forming...
www.thingiverse.com