If you're reading this post, then you're the one who says the shop is bugged and needs a fix. Think a bit more next time because the the solution for this problem is easy. You just need to Zoom In / Zoom Out (Ctrl + +/-) enough while the window is opened and click on the item you want to select / buy. Finally just refresh your game.
PS: This isn't magic.
Yes, it is sort of a fix but the shop is still meant to be small and with categories, not one.