They may not actually exist - alloy bars aren't strong enough to cope with the stresses of winching.
I bought a universal steel cradle from fleabay and cut it down to fit. I'm having custom brackets made to accomodate my BL, but if you don't have to worry about that just figure out a way to bolt or weld the cradle to the bullbar brackets. Also an idea to tie the cradle back to the chassis at a few other points, as the stock brackets are only held on by 4 M8 bolts.
Pics etc here:
http://www.auszookers.com/index.php?nam ... &start=150