Hi Col,
I guess it depends on the counterweight bar diameter.
Claudio from A.E.C. is a 10Micron reseller and he has stainless steel counterweights in 30mm, 40 and 50mm bore diameter sizes. There are no prices on his website, so you may have to ring or email him.
http://www.astronomy-electronics-cen....au/index.html
Cheers
Bill