Try adding this game to your steam Wishlist from the search drop down page then add to cart without going to the store page I bought a credit card required verification game just now. (And I don't have a credit card)
Go to steam, search this game in the search bar, hover mouse over the game and click on the 3 dots, (3 options - Add to your Wishlist/on Wishlist, ignore and store preferences ) click Add to your Wishlist, now go to your Wishlish find the game, click add to cart, then buy and install.
This work around ain't going to last long make use of it. get what you can.