That's custom made, but I recognise the keyway. It's likely a custom device made by LockForest. I made a thread here
See etsy link below https://www.etsy.com/uk/listing/1413430478/handmade-mens-chastity-beltstainless Interesting in that it looks like you can take the cage off whilst still being locked into the belt.
Looks like he's playing middleman, you can probably cut down the costs by contacting the manufacturer directly. Granted he probably doesn't speak english