This one, which with postage and VAT is £29 from RD:

http://www.rallydesign.co.uk/product_info.php?cPath=608&products_id=4063

you will need to buy the corresponding bar to go with it.

http://www.rallydesign.co.uk/product_info.php?products_id=4062

The detente mechanism that makes it click is not working (I accidentally took it apart and the springs and ball bearings shot out). It could be fixed quite easily, nothing is fundamentally broken.

£15 posted

Edit: I should note it works fine for adjusting brake bias, just doesn't click into position.

[Edited on 12/11/14 by rodgling]

U2U'ed.