I've been using an old golf bag cart quite successfully. I bought mine for $10 at a used sporting goods store. A couple of tie down straps is all it takes to secure the deer to the cart. It's nice because it folds up very very compact. Not a perfect solution but has definitely saved me some backache!

Honestly, the cart could use some simple mods to make it perfect...
* It needs another crossbar in the middle of the rail. The one at the top and bottom is not enough. The deer doesn't sit squarely enough without a middle crossbar and sometimes slips down onto one of the wheels.
* a cable running between the wheels (like an axil) would add some strength.
* Even though I've had no problems so far, larger wheels might be beneficial for rolling over some sticks, logs, etc.

-Mike