Dimmers do not adjust temps they control power. If you drop the power then the temps follow but it is separate from the temp. This means they work super super well as long as your room temps are completely stable.

Most hardware stores will carry dimmers they are not a specially item. I think I read that your ambient temps were quite high so a dimmer would have to be watched closely. If your dimmer is set to 1/2 power and at 80ºF and that gives you 90ºF hot spot, if your room temps go to 85ºF your hot spot in theory would be 95ºF in my experience it is often higher like 97 or so.

They often need to be adjusted as the room changes my rooms alter quite a lot during the day so in my case they are a very poor option but still better than nothing!

One option is to set the dimmer (rheostat) to give you 92-3ºF at the hottest part of the day and just allow it to drop the rest of the time until you can arrange something else.

I'd offer to help you out with your T-stat problem but i am in Canada and it is likely to be impractical. Did you look on ebay?