Truth be told I have 2 Thorens TT and get great enjoyment from doing my own repairs. Having extra parts available represents more opportunities to fix additional TT's. Pssst, don't tell my very gracious and ever suffering wife.
Going the gunsmith route may be possible, I'll be seeing him this evening. The pulley assembly consists of 4 pcs; two pulleys, the slip clutch and a coil spring. The slip clutch is the damaged part.
The only way to get dimensions would be to take them from my TD-160. This means having both TT's down for an indeterminate length of time. Finally, the slip clutch is the only piece that does not lend its self to tunrning on a lathe. It will have to be made on a milling machine. This last part I discoverd last night after disassembling the motor pulley assembly.