LOL! The portable AC units?
They seem to be getting less expensive every year.. just not in July!
They are reported as generally less efficient; yet, if one can get it situated and plugged in, it is likely to be more efficient than any window model not yet installed. Overall, they are more expensive. Once in awhile there's a deal here or there.

I am glad my DH puts in the window AC units! I would not be able to do it, as much as I hate to admit this! Far too much pain, weakness, spasms.
No can do! My arms/hands are at least as severely affected as my legs/feet.

Are your bare feet touching any substance that may cause worsened burning?
Is the a bare foot touching a bed of a shoe/sandal it might otherwise not directly touch in cooler weather? I ask this because my skin reacts to so many materials! Just a thought.

I hope you get help with the AC soon!
Hoping you feel better.. pronto!
~DejaVu