Hi
Have a look on ebay for them, although prices on eBay have gone up quite a bit over the last year but something like this one would do you
http://www.ebay.co.uk/itm/Ultrasonic-600ml-Cleaner-Jewellery-Dental-Watch-220V-/320749315101All you add is the appropriate cleaner for the type of paint you use, Acrylic, Enamel, Cellulose etc. For Acrylic I use Iwata Media Cleaner mixed 50/50 with distilled water, and for enamels I use white (Mineral) Spirits.
This is the one I use, I like the option of it having 2 different power settings, although I only ever use it on full power.
http://www.ebay.co.uk/itm/AOYUE-9050-Ultrasonic-Cleaner-microprocessor-controlled-/260816833032A quick note if buying from Hong Kong or China, check the postage charges, some will do it for free and some will charge quite a bit, its often cheaper to buy an expensive one and get free shipping than it is the buy a cheap one and end up paying high postal charges.
Hope this has been of help
Paul