Schematics on the log ain't real complicated. Just take a look at one. For stones, you have two options really - use rocks you find lying around that are sort of round, or learn how to make your own and rent molds. That'd be least expensive, though you can buy them too. If you're near Mass, contact Murph at Total Performance Sports for molds or stones, he'll take good care of you.
The yoke and farmer's walk aren't real standardized. For a design for farmer's walk handles, check out this article:
I made a pair for about 30 bucks (a friend had a drill that worked), but you might want to pay a little more and get real sturdy pipe.
Not sure about the yoke, I don't know what thickness steel you'd need and all that.