Use one of the thermoelectric coolers such as this one :

http://www.amazon.com/exec/obidos/ASIN/B0002J1AE4/ref=pd_sxp_elt_l1/102-9030747-
4827357

    Any of the concentrates such as Rodinal, T-Max, HC110 could be poured into
small glass bottles for one shot usage. The 2 & 4 ounce amber PET bottles
available at :

    http://www.specialtybottle.com/index.asp?PageAction=Custom&ID=43

    Concentrates keep well when stored in full bottles and shouldn't have any
difficulty with your circumstances.

I've lived and shot in the desert Southwest US for over 30 years, and
all I've every used to store film in the field is one of those little
"6-Pack" coolers in the car.  (And I try to park the car in the shade.)
As far as carrying film while away from the car, I just keep it in the
camera bag and out of direct sunlight, if possible.  Never had any heat
related film problems.

After shooting, the film gets returned to the cooler or the fridge in
the motel room.  I keep it cool until I process it.  If it's going to
be weeks or months before you can process, freeze the film, but put it
in airtight, sealed bags to keep out moisture. When ready to process,
defrost it at room temperature still in the bag to prevent
condensation.

I don't store any chemistry mixed or otherwise in the fridge.  I store
it where the temperature and humidity are reasonably constant, just
like it says to on the package.

All materials benefit from lower storage temperatures.