Mites are very stubborn critters; a good thing to know is they like dry and dirty (dusty) environments. If your plants are outdoors, a good washing once a week with the hose goes a long way to controlling them. Inside you can do the same by putting them in the shower.
I treat mite infestations with Bayer Oberon; but I doubt the home gardener can get it. Ask your local nurseryman; Oberon may be available under another name/concentration. Missing that, a good horticultural oil will knock down the population to a point where you can beat them manually... note you will need a 10X glass to see them; and every grower/gardener should have one.

I did a search for Spiromesifen.

Wow, is it expensive!

http://store.doyourownpestcontrol.com/forbid-4f-ornamental

Here is a link that might be useful: Forbid - Spiromesifen

Expensive. yes, but you only need a very small amount; and it stays on the tree for up to 15 days. Very effective.

Have you tried a 50/50 mixture of alcohol/water after hosing them down and letting them dry? If your tree is not huge, it is an option. My trees are under 6' high and this mixture has helped so far - with cotton balls or paper towels. It kills on contact - but you have to have direct contact. It might not be feasable with a larger tree. I hear orange oil, diluted, is also an option.

Thank you all.
I am going to try the hosing them down and the alcohol solution. They are fairly small, shouldn't be a problem if they work! If not, I'll look into one of the products.