The lock for your year is a KT lock. You can still get them, but ve prepared for sticker shock. They are $500--$600.
There is a replacement "kit" that is intended to delete the KT lock and install a more generic and readily available Fastec lock, but if your door, latch and catch areas are in good shape, I would go with the quickest solution and just put it bajck the way it was with a new KT lock. You "may" be able to get parts if yours just had a broken pin. But changing the lock is riddled with ramifications and probably shouldn't be done unless you have to.
The round light is known as the "scare" light. Also still available, but you can upgrade to LED version. I think i paid $30-$50??
Out of Doors Mart is a good source in NC. Inland RV is in CA. Vintage Trailer Supply is great. And Airstream Supply.
Sounds like you'll be getting to know these suppliers.