Looking for heatsinks

[DiverDude]

The idea of a heatsink is to provide a large thermal mass which has as large a surface area as possible. The larger the thermal mass, the more "sinking" of heat. Most heatsinks have 'fins' since this dramatically increases the surface area exposed to ambient air. The more surface area for a given ambient temperature, the more heat that is transfered to the surrounding air.

Have you tried pricing solid aluminum plate -say, 1/2" thick ? You could make fins 1/4" deep in that with a table saw quite easily.