Well, I can't see the pics, but what if you put buttonholes on BOTH pieces.
They are flat, and don't weigh as much as grommets (do they?).
Then you could sew short ties to the buttonhole. In fact, you could USE the end of each tie to reinforce the buttonhole.

Then, to attach, you'd just lace the short tie from one buttonhole through the other, and vice versa, and tie.

I have this picture in my head... too bad I can't draw on the puter.