If you can get a heat mat and a inline thermostat for it, that is the way to go. A 1020 tray size heat mat runs $12-16 USD on amazon. They are usually rated at 18watts or so. A thermostat can run $15-20. Not too many years back, I got a combo set with both for around $23.
Fresh tomato seed set at 82 degrees will start showing emerging loops inside 3 days. Then they should be removed from heat; bottom heat on tomato sprouts will make them leggy. Old seed might take longer. I use 75-85 depending on whether there are other seed types on the mat.
Most all are made in China and look something like this:
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