Logan and Skybus Twotter ratings are done by Logan and Skybus on type using their own TRTO. Loganair I know, have in the past trained external pilots to fly the Twotter, but not many.
I believe that Flight Safety operate a Twotter sim in Canada, but that may have changed by now, so please don't quote me. May be the only one, but not too sure?!
Cheers
ACA