The Raspberry Pi M.2 HAT+ M Key enables you to connect M.2 peripherals such as NVMe drives and other PCIe accessories to Raspberry Pi 5's PCIe interface.
Rather than wasting extra money on a larger enclosure, I used the original case, although in order to secure the lid, I had to use some extra black tape to hold things in place. Not super professional-looking, but good enough for my needs.
Works like a charm and it's now amazingly fast.