Hi,
you used to be able to buy a one off payment of an area or region, with Viewranger.
That is how I got the maps I needed for my walking in Scotland. Namely at home in Shetland or walking in Scotland on the TGO Challenge.
I bought the Northern Highlands of Scotland (Northern Highlands, Orkney)
the Southern Highlands of Scotland (Southern Highlands & Hebrides)
and the North East Scotland
I may go for the years subscription if I ever do a big multi day walk South of the Border.
I got my maps in 2017 for about £15 pounds as a one off payment , discounted to anyone doing the TGO, I bought a few extra tiles to include the beginning of the WHW in 2019 for a couple of pounds.
Try this link.
https://shop.viewranger.com/product_details.php?item_id=589