You will probably have to fabricate it as I doubt bolton roll cages will be availible
Remember three things about roll cages
They have to be made with sturdy and thick gauged pipes with smooth bends(no crushed bends)
Every possible stress point has to be triangulated with supporting pipes.
Use and find the existing chassis support points to give the sturucture a good base
And finally no cutting corners these things are designed for safety and structural rigidity so
FUNCTIONALITY> your comfort and ease in getting in and out of the car.
Thank you.