Are you looking for motor spacers or spiders spacers?
spider spacers are on ebay through robot underground.
If your looking for motor spacers, use 3/4" mdf and coat it with a VERY durable and stiff epoxy. mount it while the epoxy is still "wet" or open so that your alignment is correct. Or else do what i do. Find a piece of 3/4" plastic and cut one out using a jig or scroll saw. I need them quite frequently too since the 3hp bottomless was designed for the ti basket and has that extra 1" flange on the top plate. Or if you can find a VERY good machinist. Have him trim off that flange to make a .5" top plate. You would need an EDM or wire mill in order to do so though. A regular lathe or mill will create rough edges or excess debris.
i like the plastic idea and will use that thanks... these things have given me the red ***//content.invisioncic.com/y282845/emoticons/rage.gif.0ad8a6e5565b5fddce406566fdd05149.gif