Haha I know, I can't stand it when people still try to recommend hot rocks, or especially when I see pet stores that still use them for their snakes. It's just the "old school wisdom" I guess

Anyway, as for your question, I believe I've seen others recommend putting an UTH in the terrarium (controlled by a thermostat of course), and then laying a ceramic tile down over it. That way the snake has belly heat, but doesn't come in direct contact with the UTH.