Jon,
Loricraft power supplies for Garrard pop up from time to time on the British s/h market usually for 500 to 600 UKP depending on age and version.
Industrial motor controllers e.g. Siemens Micromaster 420 the cheapest variant for a driving power of 120 W (there are other variants for driving up to more than 1000 watts)cost around 250 EUR, plus programming panel about 40 EUR for different settings of voltage and frequency. See www.conrad.de in Germany, or any other electronic supplier. A guy in Brussels uses such a controller for his EMT930 idler deck, and reports great results. Though, I have not yet tried this route.
best regards, Hartmut