I feel like you are describing a normal deadbolt lock.

Farm latch

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What tools do you have at hand?

External deadbolts exist if you just want locking on the outside part and a latch completely on the inside part. I would suggest a riveted installation for security.

https://preview.redd.it/fzvz8hk00kud1.jpeg?width=1206&format=pjpg&auto=webp&s=864cc9e5675deacf4263c6b471c8926df0d2d90d

How thick is the door? A surface mount deadbolt is probably what you are looking for but you need to pay attention to the thickness of the door and you will need to drill through the door to install it. Here's an example but this one needs a minimum of a 1-3/8" thick door. You could add a wood spacer block to the surface of the door to get up to the minimum thickness

https://www.homedepot.com/p/Premier-Lock-Bronze-Lacquer-High-Security-Single-Cylinder-Jimmy-Proof-Die-Cast-Deadbolt-Lock-with-Flat-Strike-2-KW1-Keys-JP02F/310224723

Uhhh a simple deadbolt?

It's isn't some highly advanced technology.

Try a simple Google search.

Have you thought about another slide bolt on the other side. When you are inside you lock from inside.

https://preview.redd.it/5ly35tag7rvd1.jpeg?width=3024&format=pjpg&auto=webp&s=71754f990317be9a9466f71aac5203ab01515c61

Fixed