Would you want to get two platies? Most of them are great with bettas, but they aren't cleaner fish. They poop like crazy, actually. The minimum is 10 gallons, but I think you will be okay as long as you keep up with the water changes.
LOL I posted at the same time as LTB.
~ Fireheart ~ Spikefin ~ Male Bettas ~ Dalihla ~ Lizzy ~ Female Guppies ~ Sir ~ Boss ~ G6 ~ Prayer ~ Male Guppies ~ Squirt ~ Male Dwarf Gourami ~ Reginaldo ~ Regilina ~ Strange ~ Stranger ~ George ~ Mystery Snails ~ Zeus ~ Poseidon ~ Hades ~ Hermes ~ Apollo ~ Serpae Tetras ~ Bristol ~ London ~ Beverly ~ Female Platies