Cherry has made keyboards with blank keys but they are only sold to companies that are supposed to print their own layouts on them. Only a very few of them have come in hands of enthusiasts.
The second-generation DAS Keyboard was such a Cherry G80-3000 with blank black POM keys, not PBT.
If the requirements had been tenkeyless, then I would have suggested a "Navy" very dark blue Leopold's ANSI set + a Cherry ISO Enter key, which is what I am using on my TKL keyboard right now. The Leopold set contains a 1.25 key for left Shift and the key next to it, but is one key short for a full-size ISO: the home-row key next to Enter has to be borrowed from the numpad.
My camera is crap. I plan to dye the Enter key blue some time later.

Edit: The leopold keys are sold by Widebasket on eBay. They are discussed
here.
I guess I could sell you a mid-grey Cherry Enter key (with a lasered legend) and the remaining numpad-key from my set, if you want to go this route.