Wayne, thanks for the kind comments on my build - it certainly was a bit of a roller coaster along the way, but other than a few small unexpected things since then that have caused me to take it all back apart again (minor oil leak at the head gasket, cracks at welds for the rear fender mounts), it turned out well overall and will be better (hopefully!) the second time around... it's a labor of love.
There are quite a few yards all over the US that still have some used 450 parts, but finding good salvage yards is a task even with the internet to help as many don't have websites or advertise that way. There's one you might try that a few members have gotten some parts from - his name is Dan Foukes and his phone number is 586-872-3515 in St. Clair Shores, Michigan. There is a fair-sized yard near me in Florida but all of his stuff is outdoors and quite deteriorated, so I haven't bought anything from him since walking his yard (water in the bottom ends of engines, rotted seats and seat pans, etc., etc.). Good used parts are certainly getting harder to find for our bikes.