Its going to be really tough with the platform dimensions you want.
The two other than a LW that come to mind are from Gorilla (one of their Elite series with the net seat) and an old Loggy Bayou Pro Series hangon - I don't know if they even make it anymore.
Another option would be Muddy - in fact if I had to get another light hang on, it would be a Muddy - it's almost a perfect copy of the LB Pro hangon for less money.
That said, hang ons should be a set and forget item, if you're planning on same day hunting and mobility, I LOVE my TreeSaddle. It does take some getting used to and practice, but they work great. I missed the largest buck I'd ever seen out of one - my fault, nerves got the best of me.