If you build a ten foot wall to protect yourself from thieves, they just buy an eleven foot ladder.
Fortunately, I live in a very rural area and don’t need a locking pin. But I do have one. Both pins are only in place for the duration of my towing needs, which is generally only hours. Both are stowed in a tote inside my 4Runner.
My locking pin is simply a cheap Harbor Freight pin, which I’ve had several years. I don’t think it’s ever seen a raindrop or snowflake, so I cannot comment on its durability. Being a Harbor Freight item, I doubt it has any durability. But it’s worked for me.