Hello Stompetower
The rash you are describing is very typical irregardless of the type of sauna you use. The same rash has been reported from many users of the very expensive fibreglass saunas as well. If you go to Dr Pressman's group on Yahoo you will find this has been debated ad infinitum for years. The general consensus is that the rash is indeed caused by escaping toxins/heavy metals and will go away in time with reduced and /or less intense use of the sauna.
I don't think there is any other manufacturer than China for the inexpensive sauna tents. We built one from wood once just to try it but it was so bulky and cumbersome it didn't get used long.