I'm assuming by an Adventure 203 that you really mean a 205 Adventure? I think your best bet would be to call these guys linked below or have someone locally do a T-top for you. Unless someone lived close by and had one that they weren't using then I'm thinking you'd pay a ton for shipping or have to drive to go get it.
GW Performance Welding provides professional welding and fabrication service
www.gwperformancewelding.com