Piraeus Bank, Greece’s fourth-largest lender, has agreed to buy almost a third of its smaller rival Proton Bank via a share swap – at a cheaper price than a previous agreement canceled last month. Piraeus agreed yesterday to buy the 31.3 percent stake from Proton’s major shareholders, offering one of its shares per 8.25 Proton shares, in a 24.8-million-euro deal. The previous arrangement, which fell through, was based on a swap ratio of one Piraeus share for every 5.5 Proton shares. Piraeus and Proton Bank canceled the previous share-swap deal after Proton opted to take part in the government’s 28-billion-euro bank rescue plan, which includes measures to boost capital and provide liquidity. Piraeus shares reversed mid-session losses to end 2.45 percent higher at 10.86 euros on the Athens bourse yesterday, with Proton closing flat at 1.15 euros.