No need to go overboard on wattage Norm, I find that one of the little Aldi 600mL/50W [input power] units works OK for small Items. Specs, watches, small carbies etc - I've actually got some rifle cartridge brass in mine being cleaned of tarnish, right now.
The thing to realise is, you're not necessarily limited to just the sizes that will fit in the bath itself - it's possible to use a taller plastic container. 'Flexible' containers like milk or bottled water bottles work best.
You just stand it in the bath, fill up with your water-based cleaning solution, and fill the bath around it with plain tap water.
If you do decide on a more powerful/bigger tub unit, Jaycar Electronics sell a 2.5L/170W one that's good value.
