Could talk with someone at Teknomotor to see what they recommend for a VFD for the specific model. Single phase or 3 phase availability in your shop. Any electrical supply or electrician should be able to come up with needed cabling for from panel to control box, control box to VFD, and VFD to spindle (shielded for this one).
VFD would need to have the option of rpm control via RS. I happen to have one of the SB speed controllers for sale if needed.
Scott
"It’s easier to fool everyone than it is to convince them they've been fooled" - Mark Twain