We can indeed offer you a spare wheel for your Demco Kar Kaddy 3. It is a chrome wheel rather than white.
The part number is # DM11574. It is a 14 x 5-1/2 inch wheel with a 5 lug on 115mm bolt circle (which is the same asa 5 on 4-1/2"). I've confirmed with Demco that is indeed the correct replacement wheel. You'd want to use a ST205-75R-14 Load Range C tire like part # AM10234.
The # AM31985 you referenced wouldn't work well for you. It's a 13 inch wheel, not a 14 and the offset would... view full answer...