Depending on where you are in the world, you can always check eBay and craigslist for such components. You can also looking at Google's Product Search (a.k.a. Google Shopping) by entering the search terms of what you are looking for. Such as:
Why 486 or Pentium 1 you might as well at least go for a Pentium 3 you can find a ton of cheap P3 stuff in fact I have a few P 3 motherboards with ISA slots And I believe I have 3 or 4 Pentium 3's around. PM me for more info.