I could only find the smallest numerical rear sprocket from JT Sprockets in 48 tooth. I would have had to order it from the UK. I found a sprocket maker in the US who can make most any front or rear sprocket, and since they were sort of familiar with the Derbi Senda 125 R, what TMEC 200 and 125 enduros use as their clone, they custom made me a 40 tooth rear. I just received it today, so have not had time to install it, but visually, it seems to be dimensionally correct for the bolt pattern (the stock 56 tooth sprocket is still attached to the bike since I need to ride it!). The 125 TMEC, or Derbi Senda 125 R might not be able to pull this sprocket (the 200cc TMEC might not--again, have not had time to try it), but if it does, other 200cc enduros with this sprocket might want to consider one. Someone with more knowledge of bikes than me (pretty much anyone) who thinks these might be good for the 125, might be interested in one, too. I ordered them from Rebel Gears out of Tennessee in the US. Since they made mine (and assuming it fits), they have the pattern in their system, so should be able to easily replicate one. However, let me try mine to see if it fits correctly, and works properly. If it works, call or email them directly.

http://www.rebelgears.com/officialrebelgearshome.html