Have a look here
http://search.stores.ebay.co.uk/Jaso...173167QQsofpZ0 he sells a lot of bits for the DF-03, both standard and hop-ups
One th9ing I noticed is he does the Kawada conversion kit which means you can use pretty much any 48 pitch spur on the DI. I couldn't find the centre 1-way set on his page (but he does do the front 1-way) but if you look here
http://search.stores.ebay.co.uk/Vell...126231QQsofpZ0 this guy does the centre 1-way and again, most of the spares and Tamiya hop-ups. I've bought pretty much everything for my DF-03 from these two guys, apart from the 3 racing stuff which came direct from 3 racing.
Hope this helps,
-Steve
EDIT just noticed that neither of them have the Tamiya slipper conversion listed at the moment.