Members of the Commission who are not full-time officers or employees of the United States and who are not Members of Congress shall, while serving on business of the Commission, be entitled to receive compensation at rates fixed by the President, but not exceeding the rate specified at the time of such service for grade GS–18 in section
5332 of title
5, including traveltime; and while so serving away from their homes or regular places of business, all members of the Commission may be allowed travel expenses including per diem in lieu of subsistence, as authorized by section
5703 of title
5 for persons in Government service employed intermittently.