Sure thing, let’s keep it simple and low‑cost. Start with a standard barrel lock and swap out the tumblers for a set of pin‑tumbler pins that line up only with your custom key. Instead of buying a whole new lock, just take a cheap skeleton lock, re‑tool the pins, and add a small, cheap keyway plate. Use a tiny brass plate to add an extra notch pattern—this is your “specific key pattern.” To make it tricky, add a secondary lock‑bar inside the barrel that only releases when the pins are in the exact right order, but keep it short so you don’t need a whole extra bolt. Cheap steel, some basic machining, and a little ingenuity, and you’ve got a lock that’s both tight and budget‑friendly. Good luck, and remember to keep the key safe—you don’t want to be the only one who can unlock it.