Hi!
My old set was the same kind, and my drumming teacher said he considered buying a custom tom for my birthday (he's also a very good friend beside being a teacher

. Anyway, when I asked him if that was possible he thought that it was, but it would require a special order, and would probably cost a s**t load of money

He intended to go to a shop representing Sonor and make the order through them. I suppose you can contact Sonor directly (here's their web site:
http://www.sonor.de/) and order from them. You might encounter a problem because I heard that Sonor doesn't make the Force 2000 kit anymore. I haven't tried is myself, and my teacher also didn't try it, so you should take it all with a grain of salt
Good luck!
All the best,