C&C marine Towers in Cape May Court House (www.ccmarinetowers.com) has a gallery tab; about four rows down is a photo of a late model GW 18 with a T top they made if anyone's interested. As for me, I'm heading there Monday.
I installed a T-Top on my 2004 180 Sportsman Grady 2 years ago. I purchased from FishMaster in North Carolina. You can find them online. The total was $995 which included free shipping and no sales tax!! This top is fantastic. It's adjustable but once you tighten it down there's no movement at all. It's every bit as good and quality as you'd pay for a custom made for $2500 or better!! I think their price has increased a couple of hundred dollars more since I purchased mind. My sons installed mind but I put it together. You won't be sorry!!