Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Hope you have some seriously deep pockets because that is going to cost a fortune!

Here is a place that lists on eBay offering 4" & 6" diameter copper pipe, however they don't seem to list 5" diameter.

https://www.ebay.com/itm/141461211975?

Somewhere else I did see 4" end caps that were rather expensive as well.

Perhaps a dedicated metals supply company like McMaster-Carr or Speedy Metals would be a better source?

Good Luck in your search!