dad picked one up last year to put in the new plot we did behind the house.
it worked really well, once we dialed the spinner in to the correct gap anyway.
it was right around $200 but dad cant recall what brand it is off the top of his head and his knee is acting up so hes not up to heading out to the barn to check.
its a barrel style that just bolted onto the back rack, kind of like the Moultrie does, but without the feed gate they have for product dispensing control - as mentioned you just moved the spinner up/down until you got the proper gap to give you the drop ammount you wanted.
edit #2:
http://www.ontimefeeders.com/products.php?pid=34on Time Bumper buddy model #22000 spreader is what we've got. Dad found the paperwork for it in the house
HTH