Need product recommendations-very small heating pad

Calling mouse/rodent/small animal researchers:

Im looking for a very small thin heating pad, nothing fancy (no thermistor, control box), less than 75cm wide. This is the best ive found but im not sure how hot it gets. Eventually we will splurge for a proper heating system but for now we are just doing preliminary testing for a new setup.

Let me know if you have had any success finding or making your own. This pad needs to fit into a small stereotaxic frame, maximum width is 75cm, max length ideally 135cm but maybe can go a bit longer. Also thin enough to not displace the animals position too much. Thanks!