I had a heart attack two and a half years ago. I am still paying the hospitol and doctor bills. Can I get a supplemental policy that will cover some of these charges if this happens again>

Its possible. Some frown upon "existing conditions" but some are more forgiving.

You're best bet is to call various companies and ask for a quote, most if not all provide that for free.

You might be able to but won't cover expenses already incurred. If you are successful (and I doubt you will be unless you are part of a big group of individuals and the insurance is not medically underwritten) in finding insurance for future such expenses, be sure you understand the details, exclusions, limitations.