If you're really into it, there are usually a few on eBay. A few years back I almost picked one up for my dad as a fun gift; he worked for IBM for 25 years and much of the later years were focused on the AS/400. He spoke quite fondly of it.
I wonder what the licensing situation would be – especially if they'd wiped the disk. Although I'm now tempted to look that up...
Here's a deep dive book on the architecture of the AS/400 up to the PowerPC port, written by Frank Soltis, one of the main people behind the system.