If you want a raised vented floor it is probably just as
easy to custom make the floor. We're not talking fine carpentry
here.
2 x 4's laid on their side, about 16-24" apart with 1 x
4's at right angles would do it. If you want to be sure that you can
remove them to use the stall for horses, just make sure that you make it in
say 2 pieces that fit together and easily come up and fit through the
door. Probably no need to tie things together on the bottom like
shipping pallets. You will not be using a fork lift, and the 2x4's are
not on end.
They could either be nailed together or screwed with 1
1/2" dry wall screws.
Another possibility, there are companies that make duck
boards out of plastic that snap together to make a raised dry floor for shower
rooms and industry. Sorry I don't have a web site etc. I haven't
purchased in 20 years. At that time they were available in about 1'
squares.
Ed
Ed & Wendy Hauser 2994 Mittower
Road Victor, MT 59875