I still say there is something that will work with minior mods like relocated mounts. Take the bike to a dealer and see if he'll let you hold a few plates up to the frame for a test fit. Did you actually try to fit the 300 plate to the 250F, or at least hold it in place with a jack and locate any mount changes? I ask because we had a 125 GG with one and it also fit the Pampera easy. Very little available for those bikes as well.