I bough 99.9 pure lidocaine to use for a tattoo, but don't know how to mix it or what to mix it with.

99.9% lidocaine?: I am not sure what you bought. 99.9% lidocaine would likely be a powder that a drug manufacturer would use make lidocaine for topcial use or injections. Too much lidocaine, even if you apply ti just to your skin can kill you by causing your heart to beat abnormally. Don't risk it. Go to your doctor and ask him to have a small amount of topical medication that you can use with each treatment.

Due to liabilities: Issues I can't specifically recommend any particular home compounding, but you're best bet may be to go to your local tattoo parlor to see if they have any recommendations for you. Again, I would encourage to you avoid mixing this "stuff" at home home.