I require hardware to build a controllable heat bed with maximum dimensions of 400mm x 150mm with a controllable heat range of 30c to 70c. It will also require the corners have screw down holes as it will be placed into a wind tunnel.
It sounds like you might want a silicone heater mat of some sort. I think it’s unlikely to have holes, but you could cut a piece of aluminum to cover the pad and hold it down.
Good luck with your project!