Ok, i give up at the moment, i've done searches on everything to do with CJ4A also on Asti RS RX's , I've searched Asti, Asti RS mivec, Asti rs cross brace / brace / radiator brace / support brace radiator / strengthening bar / blah blah blah and couldn't find anything listed. I did find a mention in a english/irish performance site, they did mention that they had one fitted, nothing else, not even a pic.
I not saying it didn't exist at some time as an option from a 3rd party supplier to OEM (ie: similar to likes of JDM etc) but i can't see it anywhere on the net now, back in the 90's the internet was only getting a hold and many suppliers did not have anything remotely resembling a decent web site / online parts catalogue's ect, so i'm not surprised info is extremely difficult to find on these.
I've learnt the hard way since the 70's that many manufactures did not always advertise everything they did or special vehicles (SVO) parts/accessories that they made over the years, so just because you can't find/see/locate something doesn't mean it did or does not exist.
With those pics above you can see that the welds look at bit rough indicating someone repaired or fabricated them at one time, but some of the other pics look good quality non OEM or OEM as the case may be.