We don't know we're born! There must be a greater choice of new and used parts these days than ever before. From dealers' new old stock to repro stuff of dubious quality it is all out there... plus used and discarded parts that turn up, and that's only the stuff advertised. Bikes are asleep all over the world just waiting for their turn to be restored or stripped down and the parts recycled.
ebay is a good place to start, along with autojumbles, bike shows, spread the word, go prospecting. Forum trade and service suppliers are all worth a look.
Non runners, abandoned projects, no papers, damaged, vandalised, barn finds or dumped these bikes attract almost as much as a tatty but complete runner, and there are plenty of these "Just back from the States" Here it's the depth of the pocket that is the stumbling block. The downside is that as values increase, more parts come available as the economics make more sense, but this is no longer the cheap hobby of my youth.
As for perfection, it's a hiding to nothing. You can't ride it without worrying, go for a static display bike that will cost a whole lot less to build up.
Swarfy.
