You could do worse that track down a copy of Richard Ballantine's "Richard's Bicycle Book"/ "New Bicycle Book" / "Ultimate Bicycle Book". Though not perfect, probably well suited to your aspirations (I see you have a TIG welder and a club hammer so you must have a pretty good idea of how things go together).
There actually aren't that many generic nuts and bolts on a bike. For instance, when you find some new cotter pins (specialist bike part, comes in more than one size) they will each include a matching washer and nut. There are a few generic bits and pieces like cable adjusters which you'll find on auction sites or your local (old-fashioned) bike shop - but as you point out, you'll need to know the name of what you're looking for if online. In some cases, you simply won't be able to find individual spare parts as the manufacturers either never sold them separately or have since gone out of business (Weinmann being a great example: used to supply all the spare proprietary washers, bolts etc for all their brakes, now gone) so you end up having to buy a whole new (/2nd hand) unit to cobble for spares or swap out. Exception to this is ball bearings I suppose. Your best bet may be to post pictures here and just ask. It seems that RetroBikers are unusually helpful and generous with their time and contents of their spares tins.
You are pushing it a bit to describe yours as a "racer". "Sports bike" might be about the limit. Nevertheless, determined as you clearly are, I'm sure you'll find all the parts you need, even it the end result is a bit like Trigger's Broom.