You have to look harder on Etsy for the 15mm sellers because they are there.
I purchased the below (arrived today, excellent quality) from a seller called XYZaxis on Etsy. Though he is on break atm due to high demand.
There is also a new seller called Highlands3DPrintsUK who have just started up, I've ordered from them so will be happy to say whether it's a quality print or not, though they sell prints from a different company (not Printable scenery).