SEM PPC Adwords MSN management

We have been using ppc for 7 years now through adwords, msn, and yahoo and others with our health products. The accounts have done well over the years but I no longer have time to manage them. I am looking for someone that I can pay either a monthly fee or a percentage of increased profits from these campaigns. This will definitely require someone with a lot of experience as we are past the stage of experimenting and do not want to waste money on the accounts. Please let me know what you are willing to do and what your track record has been at improving others campaign performance. Emphasis will be on adwords but we are open to other channels as well. Thank you