Sounds like a job for a 3D printer if ever there was one.
Somewhere in your area is a person desperate to use his/her new $5000 Solido machine. Getting the 420's scantlings into CAD would be the hard part. Could model one in clay and laser scan it? Maybe Vanguard could supply you with a scaled table of offsets?
Mount plastic 420 to a wood base, ta-da. Fun trophy. A CNC router could rough one out, too, tho there would be more cleanup work.