Well yea, ok I haven't got this built yet, but I planned it all out in my head this afternoon while out mowing in the hot sun. But I have a JD-3520-Cab with AC and you pretty well need an AC Cab for this.
I generally carry a bottle of Coke in my cup holder but each time I change direction, I have to keep switching it from side to side or put a heavy leather glove over it to keep the sun from heating it.
Even tho it's not yet built, I've examined things and feel it will work. Just a simple couple of feet of clothes dryer hose, (or some such material), easily connected with a couple of garbage ties at one end of the hose to the closest AC cieling vent. The other end, (bottom of hose) fits loosely over the Coke bottle,...can or other drink container. (Loose for easy access).
Now I figure that should keep your drink pretty darn cold on a hot day. Simple enough to lift it up or sweep it aside with an elbow to get a cold drink and slip it back on to keep it cold.
I don't think you need anything too tight fitting,...heck my first idea was just a piece of coat hanger bent to hang from the vent and hold the Coke bottle on its side like a cradle. Driving along holding the bottle up there (by hand), got it cooled down over time,...but my arm got sore and tired. So my poor inventive mind kicked in and I guess that's how many things get invented.
So I'll get working on it and no doubt refine it as I go,...but if anyone else gets ahead of me, please post some pics for the rest of us. UNless of course you think it's totally loony-tunes,...either way, what do "you" think?
I spose if it works well, somebody will manufacture them in China, paint 'em red, green, orange, blue etc and sell 'em for plenty at the dealers?
CHEERS !
. . tug