[cmorr (OP)]

Hello,
 I'm looking for a super compact non-toxic endothermic reaction that results in cooling 20 ounces of fluid where the heat is transfered through radiation and not convection. Thus not altering the 20ounces of liquid chemically, but still resulting with a 20-30 degree(F) drop in temperature. The reason for non-toxic is if the chemicals do mix it must still be safe to drink.

[CliffordK]

A place to start looking might be the "instant cold packs".

According to the notes, they have traditionally included a mix of ammonium nitrate and water.  The notes seem to indicate that it is only moderately toxic at pretty high doses, with the LD₅₀ about 2 grams per kilo (for the salt).

I don't think I'd want to drink a lot of it though.

There is also an ammonia nitrate free InstaKool™ Instant Cold Pack consisting primarily of Urea: (NH₂CONH₂) & Biuret: (NH₂CONHCONH₂), PLUS Water.  The published LD50 for rats and mice is around 11 to 15 g/kilo (of the solids).  That is a LOT!!!

I presume it just gets pissed out in the urine. 

The MSDS does list some GI symptoms, but they tend to be quite conservative.  Still, I'm not sure about eating it.

[CliffordK]

Urea is apparently more digestible than biuret.  However, both are apparently used as a cattle feed supplement, although it is also apparently more toxic to cattle than other animals.

Assuming the kidney function is fine, perhaps pure Urea + water might not be too bad.

Ok,  I'm seeing notes:
600 ml water + 400g Urea will drop the temperature from about 20⁰C to about 3⁰C.

However, that would be A LOT OF UREA to eat.  Even if you dropped it down to 60ml water + 40 g Urea, it would still be quite a bit, but perhaps more palatable (occasionally).