Anyone know where to get these cutters? 

Don't know who did the cake to give credit.

AAre these from marvelous moulds?

I don't think so.  I looked there and didn't see these.

These look very flat up close and marvelous molds are thicker.

By the Honey Crumb Cake Studio:  honeycrumb.com

Pretty certain it's a stencil.  You can see the irregularities in this photo--and no one could ever get those all that perfect  (http://honeycrumb.blogspot.com/2012/08/pink-magnolias-cake-for-world-trade.html):

AThank you Honeycrumb. I couldn't get a real close view of the sides of the cake. I think you are spot on. Definately looks like a stencil. Thank you so very much for the photos. I will definately rethink doing this now.

I finally found a good photo of Marvelous Molds double wedding ring overlay.  It is very similar, but not quite as refined as the stencil.  With piped dots in the center, it would probably do very well.

http://www.sugardelites.com/Double-Wedding-Ring-Onlay_p_1810.html?referer=mailid:14

by by Danielle Gray as shown on the sugardelites.com Customer Corner

AThanks so much for the photo maybenot. I didn't know there was an onlay in this design. It's just what I was looking for.

AI vote for tracking down the stencil, unless you and your client don't mind the pieces of fondant. It will be a different look, I know you know that, but it won't have that same sleek flat look to it with the mold.