Loodgieter/Plumber needed

Hello, I would like to install a small hand wash basin in my toilet and I am looking for an experienced plumber. The toilet currently does not have a sink. I believe the water supply may be connected from the existing toilet plumbing, but I am not sure how the drainage should be installed. It may be possible to connect the waste pipe to the existing drain through the wall or via the toilet drain, or it might require drilling into the floor. I would appreciate your professional assessment. Could you please let me know: Whether this installation is technically possible. What solution you would recommend for the water supply and drainage. An estimated cost. Your earliest availability.