I probably paid way too much for my coin box but I figured since I was already way OVER budget I might as well spend some extra money and get that authentic sound from my coin box. My wife thinks I'm crazy but I told her when you put the coins in the slot and there is an empty coin box it has to sound like it did when I was younger or what is the point of building this thing

.
Anyway I tried to find a metal box around work and in my garage, also checked with a few friends and could not find one anywhere (everything is plastic these days), so I went online and found one but it cost around $20.00, (I can't help it, I was desperate

). I was going to remove the cover but decided to just leave it open. I made a little platform for it and mounted the platform under the coin door.
I would search around your work or ask someone before spending money on one. be sure to check the measurements to make sure the coin box will be under both coin slots. Here is the link.
https://www.shoplet.com/office/db/BDY5051.htmlhope this helps.