Ryan Vierra told me that the Old Union forks, actually the old Old Union, are the best as they are thin but still have amazing strength.  Get a three pronger that isn't really thick, take it to a grinder to smooth and thin out the prongs and sharpen the points, buy or borrow a dremmel and sand it smooth.  That's what I did and it works fine, I just wish I could use it better.

Takes some time and effort.

Good luck.

The hay fork is what you want.

For a sheaf, we have a bag company locally that sells burlap bags in potato sack race size (about $2-3) and I bought some polypro twine in a two-roll box from Tractor Supply Company (about $25 I think).  I was making a 12-lb sheaf, so you may need to get the heavier hemp twine to make a 20-lb one. 

I pulled it out in sections from the inside of the roll--like a skein of yarn almost--and stuffed it in the bag.  I squared off the bottom corners of the bag and ended up tucking about half the length of the bag back inside before sewing it shut with some of the twine. 

For a 20-lb sheaf, the stuffing will make the biggest cost (as with mine); some material--hay, pine needles--would cost next to nothing compared to the twine.  I wanted to make mine much more weather proof. 

I hope this helps.  E-mail me if you want and I can take a picture and send it.