firebert,
That type motor can be run with a simple DC drive. Ebay is full of them. K&B electronics makes commercial drives for DC motors. A lot depends on the motor, but for your use an simple drive will do fine.
A few comments on faceting machines - The table (disc) should be rock solid. Use a belt drive to transfer the motor power to the lap (VS is still a good thing on the motor).If you are using the motor shaft and the bearings of the motor to mount the dics on, it will have far too much side play. It may feel solid, but when doing a facet, a few ten thousandths of an inch will mess everything up. The mast or table shaft for the quill is the same. You can't overbuild these two things. For an 8" lap,I would go with a 1.5" shaft and the best bearings you can find on the disc table, and the same size and rigidity on the mast (or quill table shaft). I have been faceting for a long time, and can tell you that the rigidity is what you are paying for when you purchase a faceting machine. If you build one, you have to go as strong or stronger. Compare it to a 2X36 belt sander from HF and a Bader grinder. Both do the same thing, but for knife making the Bader will hold up better and longer. The Bader costs the same as 20 HF units, but is built 20 times stronger. Look at this photo of an Imahashi faceter and you will get some good ideas.