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They aren't hamster mites & I don't think there is any need to treat your hamster as they will just be in the cage somewhere rather than actually infesting your ham.
They can come from anywhere, possibly from wood or other natural product, it's best to freeze things like that before putting them in the cage just in case, I had something similar come from a bit of broccoli that got buried in the substrate & forgotten for a few days once!
You may have to resort to a full cage clean to get rid of them, remove wooden items & freeze them to get rid fo anything that may be hiding in them.
A full cage clean is stressful for them but I'm not sure you really have any other option.

I tend to freeze most things, wood, cork, hay, dried plant material of any kind like herbs or flowers, dry food & seeds just to be sure no little bugs get into anything!