Converters go from AC to DC. You need an "inverter" to go from DC to AC.
If what you want to power doesn't consume much power, you could get away with a fairly small inverter. There are small inverters that plug into cigarette lighter sockets that should do the trick, or you could get one wired in more permanently if you choose.
Whichever way you go, make certain to turn the inverter off when not using it because it will put a small vampire load on your batteries even when the AC devices are off.