Ryobi drill-driver, needs battery (Brantwood Park)

Old Ryobi cordless drill-driver Model HP721, with battery that no longer charges. Battery is old 7.2V Ni-Cad type. I tried the new 18V ONE+ Lithium-ion battery that came with the new drill-driver I bought, and the battery does not fit. But I’ve heard that some of the new Ryobi batteries may work with these old “blue” tools…
Offering the drill body with old battery, the charger, and hard plastic case — no drill bits or driver bits as I’m keeping those.