Some of the portable ones are actually pretty good and do put out enough infrared.

This is the company I used to work for about 7 years ago:
Chee Energy

Find the products link and click on the link for portable FIR sauna.

Theirs is $399. I would call Dr. McGee at whatever # you can find and ask him details if it will make you sweat, the temperature, etc... and refund guarantee policy.