yes they work. I have used them before especially when I was driving more off-road.
If you look in Walmart, Target, KMart or OddLot you can find them for $20 or less. You can even find them on eBay
The jewelry cleaner I have I found for $5 at a Walmart bargain bin.
I have also found them at flea markets or even tag sales.
You will have to hunt around, but they can be found for less than $20.
This link has a few: