I ended up going with a t-handle truck cap style lock. I build a simple latch plate for it on the inside of the galley. It isn’t as low profile as I would have liked but I do like that all the hardware is internal and I don’t have to worry about the hasp or lock banging on the camper.
I originally purchased a cam lock like the one’s Bill used but I was a little concerned that the 1/16th or so rim wouldn’t have enough grab to hold and not pull through the hatch. I’m sure you could make or find a washer to help spread the load a bit if you wanted to go that way.