This is for the U.S. only-
) use to sell ring weights, but I don't see them listed, write and ask. They do sell a ring handle and some guys use that, plus a link and loading pin to make a similar thing- http://ironmind-store.com/R-Ring153-Handle/productinfo/1258/
Sorinex makes a Hammer trainer that some folks like-
Bert does the Highland games stuff too, so they might carry other things too- www.sorinex.com
There's the North American Scottish Games Association that is a lot of help- http://www.nasgaweb.com/getstart.asp
And a few other things-
Steve Pulcinella, who's a member here, was/is a high level Highland guy. He runs Ironsport Gym, www.Ironsport.com
and does stuff for www.elitefts.com
. Maybe he'd know the inside scoop.
Some guys at www.powerandbulk.com
are active in the sport, so they might help you.
If in Europe, I don't know, but maybe try www.pullum-sports.co.uk
, they've been in the power sports for years and might know.