I can hardly imagine a whole elk on a single sled. Seems half an elk on a sled could be manageable by two men if the terrain allows.

For elk, I usually hire an outfitter friend to pack the meat but I always have it "quartered" and often in game bags ready to pack on the horses or mules. Since I worked for the outfitter, (actually his grandfather), I'm accustomed to cutting elk into pieces for their preferred packing arrangement in panniers. The quartering is done in seven sections; the four legs, the front and back sections of the spine cut between the 4th and 5th ribs, and the head and neck including any antlers. If the head will be mounted then the hide is caped in the field if time allows. This is also a good way to quarter for backpacking.

But my upcoming pronghorn and deer hunts are solo affairs where I couldn't justifiably afford to hire an outfitter even if one was nearby. Thus the game cart search. I did find one interesting carry system, the motorized ePack Wheel. https://www.packwheel.com/
It's pretty pricey at around $2300 and looking at videos and I wonder how well it could be managed by a 70 yr. old in typical Colorado mountain terrain. I like the idea but not the prospect of getting it back up if it tips over and down a slope.