Jim(et al),
Ive been doing some looking into this for you...Even if you have a hardened shaft I would mount a bearing.
Depending upon the diameter of the shaft, I would fabricate a bracket to hold a bearing on the jackshaft right along next to the Supercharger(about 8-10 inches away from the supercharger..more or less depending upon where you can mount the bracket too). I found this place:
Axle Bearings that seems to have good priced and a multitude of axle bearings.(they even have live axle bearing mounting kits you could probably make work)
Now you could use the perfrmance sealed version mounted into a flat plate of 3/8 stock aluminum(cut to shape for your bracket and mounted to somwhere along the head, intake manifold, water pump assembly, or wherever) with whichever size OD hole needed for the bearing, cut into it... To fasten it, just machine the hole with a postive lip in the hole(similar to how you would a sleeve for a bore on an engine block) then tap it in with a little bit of loctite and countersink through the 3/8 stock a set screw, and you should be good to go...
That should eliminate shaft wobble for .. hmmmm around $15-50 bucks, depending on the size of your aluminum sheet and if you can cut it yourself(and if you have any lying around).
Good luck!!
