This is my good old TK bucket (its easier to get a good pic of this) the pads are simply cut from a foam mat, the kind you get cheaply for using in the garden etc to save you knees..... its cheap and effective, attached very simply with double sided tape.
I did have a fan in there but took it out when i added the foam but it was a simple PC fan with an on/off switch running on a 9V battery.