Medicare will only cover a physical exam during the first year of the patient's enrollment - if that's the case, then you may be able to bill this with HCPCS code G0402. But after the first year, annual physicals are not a covered benefit under Medicare. If the patient chooses to have one, they can pay for it out of pocket, or their secondary insurance may cover it, if they have one. There isn't a different code that you can substitute. There is coverage for an 'annual wellness visit" (AWV) which the provider may offer, but that is a different service and it does not include a physical exam.
Here is a chart that lists all of the preventive services which Medicare covers:
Preventive Services Chart. Learn about codes; who is covered; frequency; and what the Medicare patient pays.
www.cms.gov