Nortel and Lucent made them at one time. I don't know if they still do. DSC was a major player before they were acquired by Alcatel. I don't know if they still are. Don't expect much from the major European vendors; they use F links there.
Does anyone know why the US went with STPs instead of F links? Last I knew, the Europeans thought it was because of a lack of processing power in the 1AESS, but the Americans mostly thought the reason Europe didn't was the hop by hop setup used there. Neither answer is very satisfactory.