What's the difference between these players?
If they share almost the same insides, then the belt should be equally too?
I have seen new belts for sale for the CLD-1090.

Does look very similar to a 1090, the belts should be the same. And in any case it's rare to see an unusual belt on a 90's Pioneer player, the loading belt on later players (D503 etc) are standard SCQ4.0.