Start with your influences. Who mixed their albums? Are they within your price range? Geographical area?
Many times the answer will be “no”. In that case you will probably need to go with a less-than-famous mixer or producer. So hop online, and do some research. Look up recording studios in your area, and listen to samples of what they have produced. When you find something you like, ask “who is the mixer”? Make a note of the great ones. Track them down, and start a working relationship.