http://www.hotseatinc.com/
Driving framework setup. Has potential.
Price For Pro Version: From $1,299
Special order item
They look a bit expensive for a bit of welded steel tube and plastic pipe joints... It'd probably cost you no more than $200 in materials to knock one of those together yourself. It'd probably be a bit stronger if you did.
The cheaper ones are even less in materials... But if you must have one off the shelf, then I suppose they'd be OK to use.
Best Regards,
Julian (Fozzy The Bear)