I know it's not a piano but I thought maybe one of you had run into this anyway.

How do you replace the key if (when) it gets lost? Are these pretty much one key fits all? Drive by organ players being kind of rare?

There are some keys that are commonly used.

Take a picture of the lock, right into the key hole and post it.

Many keys are nothing more than a tapered triangle or tapered square.

If you look right into the lock you should be able to determine that.

What is the manufacturer and serial number?

If it is a pipe organ, you will likely have to call a locksmith. You might call the organbuilder, if they are still in existence.

A few European organs I've worked with have 'skeleton' keys, while others use a more contemporary type key (like for a house). A brand new English organ here has two locks that use an unusually small skeleton key.

Perhaps keys for an electronic organ would be more consistent.