I gave up on Thermorest pads and started using Ridgerest foam pads because of the leakage.
But, for what it's worth, here's what I've done over the years to patch the things...
1) Thermorest patches. Which don't work all that well.
2) Shoo Goo. Worked pretty well on its own. Works better with a piece of paper as a patch. Takes a while to cure.
3) Super glue and a piece of paper. It's all I had at the time and it worked very well. Still.
4) Bike peel and stick patches. Feathered edge road patches are best. They work in a pinch but don't stay on long.

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paul, texas KD5IVP