Try this product:

TOMLYN MITAPLEX-R

It works really good. Make sure you also get the surrounding areas of the
ear opening. Those mites like to crawl out to avoid the medication.

I am a professional cat and dog groomer and what I usually do when a I
suspect a pet that has ear mites. While in the bath, I carefully apply a
small amount of flea shampoo to the outside of the ear to prevent those
pesky mites from traveling out of the ear canal. Then, with the owners
consent, I'll apply the directed amount of ear mite med to the ear. Just
to give the owner a head start on the treatment of earmite removal.

You can get this product at most pet supply stores for a reasonable price.
Usually runs about $10 or under.

I should have included in the last reply. You have to be presistant and do
as the directions say on the bottle as with any medication.

Also, get you a big bag of cotton balls and Q-tips to help apply the
product if needed and to help remove any debrie if there is any.

Note: ALWAYS use a clean cotton balls and Q-tips for each ear. Never use
the same cotton ball or Q-tip in the opposite ear!! Animals can have ear
mites in one ear and the other not be infected. Ear mites are contageous.
,
So just use good sanitary cotton balls and Q-tips!

My rescue group gets ivermectin at a local feed/farm supply store..