I do not know of any commercial pre-assembled version that has one as a standard feature, they generally follow the same reference design. You would likely need a custom/DIY build, or modify one yourself. It would probably be best to ask for information on this on the diyAudio forum. However, the simplest solution is to buy a separate O2 and ODAC. That is slightly more expensive, but it also allows to keep the option of using the O2 from battery power.