Try
http://daisybuilt.com/ for your cage. Tom built my exo cage, sliders etc, but he is known for building tube stuff from rear bars to entire buggies.
As for a transfer brace, your chassis mounts will require bracing before the case itself. As an example - Hizook at Tough Tracks has never had a transfer case ring, just strengthening added to the factory arms, solid mounts and beefed up mounting tags on the chassis. Been good for nearly 10 years now including 6 years of most Tough Tracks rounds.
What sort of driving will you be doing? I've been having fun for years with mild mods and only just bought got a car with gears and lockers.