Side-by-side? I don't think any exist, no. You could mess with TrinusVR to get it to stream video from your PC's active wimdow and display a GBA game from it, but nothing native, no.
(Also TrinusVR isn't free, there's a trial copy and a paid copy, the trial kills your connection to your pc after like an hour at a time. Additionally, it looks like ass most of the time, but w/e)