We are going to make a cook out of you yet! Lime zest is one of those things you make rather than buy, and it doesn't matter whether it comes from key limes, Persian limes, Tahitian limes, kaffir limes, etc., etc.

You simply scrape or peel off the outermost layer of the lime peel and slice it into thin threads with a knife. Whether you use a knife or peeler to remove the peel, you want to avoid taking any of the white pith underneath with it, which tastes bitter. If you have taken some of the pith, turn the scrap of peel over and carefully scrape the pith off with the blade of your knife. Then turn your attention to slicing the peel into threads. If you have a zester or a fine grater, you can skip the peeling and slicing process.

The zest contains aromatic citrus oils and adds a lot of flavor to whatever you're making without adding a lot of moisture (as would happen if you added lime juice).

Now, we have uncovered lemon zest and orange zest for sale online, packed in 1-teaspoon packets, which presumably keep the aromatic oils from dissipating. They are not inexpensive. Quite possibly you can also find prepared zest in some specialty food stores, but it is surely much easier to just pick up a lime (or lemon, orange, grapefruit, tangerine, pomelo, etc.).