This looks like its just the hardware - not the doors itself.

You're not looking for a barn door. You're looking for an exterior door for your metal or steel building. FWIW, we used garage doors on ours.

It is a storage/hobby barn.

try adding "exterior" to your search terms - https://www.barndepot.com/shop

https://www.rammfence.com/barn/dutch-and-bale-doors
I’ve used Ramm for stalls, fencing and doors. Great customer service

You look a farm places not interior finish sites .BUt IMO for your purpose you need something better than a barn door or the mice will be in there in a heartbeat .You need a good fitting garage door .

I have barn doors on a couple outbuildings. A pair of two story bay and a half ones on the barn, and four regular horse sized ones on the stable. All of metal sheeting, framed with wood. Came with the property. I did not install them. But I know how to keep them up or replace them if needed.

Look for exterior barn door hardware. In the big box hardware stores, that is usually along with other outdoor hardware or with garage hardware. Different stores can have them in different places. If you have a farm supply store nearby, they also are likely to have this stuff in stock. Ask a worker where the exterior stuff is. If they take you to the interior stuff, say nope, need the outdoor stuff.

Tracks, wheels, stops- the stuff you hang the door from and roll it around and the stops are to keep the bottom from flapping out. Typical inside locks are hook style, but you can use other. Yes, you want a way to lock from the inside, keep it snug when the wind blows and help keep thieves out. I happen to like my metal sheeting doors, they are light and nice to use. But if you need horse size or smaller door, you can do wood. It's heavier, but can be easier to work with.

"BUt IMO for your purpose you need something better than a barn door or the mice will be in there in a heartbeat .You need a good fitting garage door ."

^^ Ditto. I just replaced two sets of sliding barn doors on my pole barn with garage doors. I FINALLY, after 10 years, won the battle with the &^!%#@* birds. Not to mention the mice population is greatly reduced (they still make tunnels occasionally), and the dust from the outdoors is now minimal. And I have them on remote openers both front and back, so much easier and faster than fiddling with sliders. Don't cheap out -- spend the money on a well-sealed garage door with openers and you won't be sorry. There are endless styles of garage doors; mine are commercial-looking, no windows or fancy trim, just plain roll-ups that match the color of the barn.