You have three options, I think.
1. Build a high voltage, low power amp.
2. Transformer couple a standard audio amp.
3. Change the motor to a lower voltage similar type.
Something like the TDA7293 can run on +-50v rails, so a pair bridged would give you +-100v swing, which might be enough. No idea on cost.
Transformer coupling works, and allows you to get something running using completely off the shelf parts, or an amp you might have spare. Changing the motor gets you the same advantages, but you've changed the motor and have to fit pulleys etc.
Somewhere I have a small program I wrote that creates quadrature sines on a PC with complete control of the frequency and phase. I used it in conjunction with a spare power amp and a pair of small toroids to persuade an LP12 to run at 78rpm.
The capacitor coupling David is talking about would be at the output of power amp.
Paul