Well, there are anchory pattern charts which are effective for this, however I don't know of any in the difficulty range you're looking for. in the 2-3star range you're still largely practicing fundamentals, so stick to charts that your right hand can handle and slowly work your way up. let your slowest hand set the pace you play at while you're in the earlier stages of developing your 4key skillset and theres a good chance it'll even itself out.
if you get into the 4-5star range, however, i can recommend some good jack and stream charts which you can use the mirror mod on for anchor practice.