Quoted from ottothebent:
I bought a 2.5 liter ultrasonic cleaner from harbor freight in 2009. It was the larger of the 2 models available at the time and cost $60.00. The price may be slightly higher now. It still works well after 4 years of use. The newer units may have had some design changes since then. Mine has a built in heating unit and a stainless steel tank liner. It has a digital timer with a range of 90-480 seconds. There are specially formulated cleaning solutions for ultrasonic cleaners, but I usually use dish soap for most cleaning jobs. You could experiment with some stronger soaps on some junk plastic parts to see what works best. Avoid any solutions that are volatile or potentially flammable. I have cleaned clock parts, metal watch bands and my metal framed glasses and it works very well for that.
Here's the latest HF 2.5L--now listed at $75:
But with one of those 20% coupons, it's back to being a $60 investment again.