I dont know about a source for the white belts but I think I heard they do have them, but where I dont know.......
The belts are the same for both models I believe but there is some adjustment in the belt so if it is a little off its okay. The only thing I have against the White FW's are the motors. They are weaker than the black ones for some reason. I know that they were the base model machines when they were sold so that might be part of it and the cases of them are made from bakelite if I remember right.
But it sounds like you did very well and congratulations on the new editions to the family!!!
Billy