Single speed 26" BMX cruisers and something that will take multiple gears are somewhat different animals. For one you will need a 135mm spaced rear end and hub/wheel to fit a multi geared freewheel or cassette. I might be wrong but most true cruisers are probably 110mm spaced like a BMX bike.
That's not to say what you want doesn't exist, it totally does but they generally get called dirt jumping mountain bikes. Quite a few companies made and still make multi geared 26" dirt jumpers. They will tend to have suspension forks though.