I agree, this prof that you have taken 3 courses with more recently would be a very good person for academic letter in my opinion. To help them out, you can also send a cover letter of things you did in the class (ex. talk about your class participation, things you did in a group, the times you went for extra help/"office" hours, etc.). Also send them your CV. The academic reference is always hard to make it personable for the writer but these extra things should definitely help! Best of luck, cheers!