2005 Spyder GT
You are a better man than me!!!You can contact other Mitsubishi sites and see whether you can find one with the MR388567 bearing kit.
Or, you can get the whole bracket, seals, and bearings from a junkyard. I'd try a site like car-part.com, which will search multiple junkyards for you.
Or, you can contact Koyo with the part number from your present bearing, and ask them for a replacement. You'll have to look elsewhere for seals that will fit.