Ironbender, since you're going to fabricate from scratch, you might check with a hyd. repair shop and see if you can pick up a scraped cyl. and use the ram for your spear. Someone with a lathe can make a nice point on it, or a chop saw can triangulate the end to work.
I'd think you'd have some farm supply store that would inventory some bale spears. If so, make a sleeve to mount it in. Then if you break it (yes it does happen) you can remove it for replacement.