Here are my quick-attach forsk on my 4100 / 410. I think the quick-attach is the same on the 210 loader.
The forks themselves are a used set of 36" forks off of a small walk-behind lift truck. They are a good size for this tractor. Anything that needs bigger forks is probably too heavy to lift with the little 4100.
The frame is 3/16" angle iron and a 3/8" flat sistered together. A couple of notches on the top of the flat engages the button that goes through the top of the fork.
I added the spacer section at the bottom for better roll-back at ground level.
For the top, I just layed the angle iron over the top of the loader bars. I added another piece down the back and perpendicular piece as reinforcement.
I used some cat-2 pins for the bottom - they already were tapered with holes drilled. Just welded them on (and was careful of the fumes from theplated metal).
I have been meaning to paint the frame for a couple of years now...
- Rick