I had an Otter Cottage a few years ago. Got tired of the bench, so I got the crossbar and a pro seat for it. Worked OK, biggest difference is the standard cottage uses a sport sled, while the pro has the pro sled. Bar had to sit a little lower because of it. Still worked OK.
Sold the cottage and the bench seat to a guy in Monroe. I saw it on Facebook for sale a couple of weeks ago. Pretty sure it was my old one because he mentioned that he had a bar to go with it. Might try to find him since he's down your way.