Arcadia-based Reid Plastics Inc., which makes five-gallon water bottles, said it will acquire a rival bottle maker in La Palma for about $50 million in cash and debt, its fourth acquisition in two years. The purchase of Stewert/Walker Co. is the latest move on the part of the family-run company to increase market share and boost its revenue to $500 million by 2000. Reid, with the help of Los Angeles-based investment banker Houlihan Lokey Howard & Zukin, said it is now the largest U.S. producer of water bottles of one gallon or larger. Driven by its acquisitions, Reid's annual revenue has risen from about $40 million to roughly $200 million. The $122.5-million financing package for Stewart/Walker also includes a credit line for future deals, the company said. According to a Houlihan Lokey spokesman, Reid is in the process of acquiring two small Eastern companies that also make plastic bottles.