I've got a piece of perspex that i used on mine to tidy my old DTRE back end up, so should fit a DTX you'll have to mod a numberplate light on it though..
no mate i didn't, got oxford ones http://cgi.ebay.co.uk/R-G-Yamaha-DT125-R-X-Tail-Tidy-Black-LP0055BK-/260764375504?pt=UK_Motorcycle_Parts&hash=item3cb6c499d0#ht_1200wt_825