JDL/Lesco is no longer making it's space saver unit. They are still made by cub cadet I believe but not available at JDL.
My locals sell sprayers by GNC. I picked up a real nice 300 gallon poly split tank last year with a 5HP Honda, pump and a gear driven cox real for a decent price.
I recommend them. I use mine specifically for tree spraying/fertilizing and it works great.
It fits like the space saver in front of the wheel wells and I have room for a full pallet. I do have a one ton duelly with the payload though.