Lots of discussion on one of my longarm lists about Batting Stands that Checkers Dist. sells. I took pictures of mine, you can probably get someone to make one for you!
You need scraps of 2x4,
a scrap of 2x2,
4 caster wheels,
and a little screw assembly that is inserted to attach the 2x2 to the base.
Check out the pictures, I put a tape measure in there so you can see the sizes. I think the end of the tape measure is covering up the screw part that goes into the base.
That little circle in the center is what the 2x2 screws into. Don't know the technical name for it.