I'm watching the Merits, but this caught my eye- https://www.ebay.com/itm/Sharp-Sigh...200014?hash=item363b9a454e:g:FGUAAOSwXMZaaIim
I ordered one, let you know how it works. It doesn't appear to have an adjustable iris like the Merit, but I bet it works better than the pin hole in the tape I tried.