The only thing that comes to mind are Honey Stingers which are honey (mostly fructose / glucose), and don't have any maltodextrin in them. You'd have to experiment and see if they make your stomach better or worse - maybe slowly start moving to them as the run progresses. But I also agree 270 kCal / hr on the run is probably too high considering your pace.

I'd also try maybe just drinking water and no calories for the last 30 mins or so on the bike.