The Italian distributor is www.amgsrl.com, trouble is you can't buy directly form their website, but I found out that www2.hibike.it/main.php also carries a range of springs for RS Duke U-turn.
I bought two springs there, one for my RS Duke and one to lower a Recon U-Turn.
The lowered Recon runs fine, the only issue is a bit of spring rattle, but the shorter spring is a good way to reduce the A to C lenght and run the fork on an older frame (a Hei Hei Ti).