I suppose the 2 sizes being referred to are 2" wide, and 2 1/4" wide. Even with the smaller size, there are several options for smaller hands. The top can be rounded off more, making it narrower. The box can be made a little narrower than 2". The buttons, which are usually put in the center, can be moved up toward the hand a little. All of which will make it more comfortable for a smaller hand.
A friend of mine has smaller hands than mine (shorter and thicker), and he had a smaller bass box made for his Regal (later model Regal. I have one too. Possibly a Weltmeister knockoff).
Another friend of mine built it for him. You don't need to get the current one refitted. You could get an alternate one constructed, screw that one on, and when you're ready to sell the box, put the old one back on.
Just have to find someone to make you one. I've never made one. I think the hardest part would be fitting the baffles and dividers in the inside, not the construction of the outer frame.