Kcender, on the Kubota Build Your Kubota site, there isn't an option for a closed cab that I saw, your dealer should be able to tell you if one if offered.
I want to get a Single Ripper attachment for my new tractor and thought about building one, but the thickness of metal required I don't have a welder that powerful. Most have said you can buy them cheaper than building just one yourself. Looking at Bro-Tec and MIF as sources.
Like you, I sure do love the Kubota TLB's.