You mean you want a bar that bolts to the chassis legs, rather than to the rear cross member? Like a 90 tow bar?
I looked for one like that and never found one. I have a Witter bar that bolt to the cross member and comes with bars that additionally bolt the cross member to the chassis legs. I regularly tow 2.8 tons on the road in a mountainous (for the UK) area, and a good bit more off road, and have had no problems.
If you're worried about the rear cross member you could always get a new one fabricated and welded in in place of the original. Given how much the other cross members have rotted on mine I think that is likely to be a necessity soon.