Cendant Corp. is moving to buy the portion of Avis Group Holdings it doesn't already own in what would be its first major acquisition since it was hurt by an accounting scandal two years ago. Cendant is seeking to purchase the rental-car firm for $29 a share, which would value the deal at about $750 million. The New York-based company already owns 18% of Avis' outstanding common shares, as well as the Avis trademark. Shares of Avis, based in Garden City, N.Y., rose $5 to close at $30.50 on expectations that Cendant will likely have to raise the bid, according to traders. Cendant shares closed off 38 cents at $12.94. Both stocks trade on the NYSE. Cendant purchased Avis in full in 1996, then sold most of its interest the following year in a public stock offering.