Any luck yet ?. I may be of help.I own a factory 1990 twr xjs and am building my 89 into a european style TWR tribute.
I've just spent 2 yrs trying to locate a complete TWR body kit. I managed to find, buy, a NOS european style kit less spoiler which I found elsewhere. ( same as your looking for ). Used examples are available in England if you look hard enough. . Problem is finding a seller who is willing to ship it as buyers are available locally. As of today, I know of a original used rear spoiler available, a dealer with a few side skirts, and the front and rear bumper covers from another wrecker. all from different wreckers.. In British pounds typical pricing is for used :
Spoiler 50- 100
Side skirts 75 -100
Bumper covers 300-350
Look at approx another $400.00 -$600 for shipping ( slow boat to china rate ) plus whatever the seller is going to charge for " crating "
You should probably allow another $1000.00 plus to refinish.
Plus whatever to install. ( These european style kits are not meant for our North american cars Many surprises during install ).
I also know of one well known dealer in Britain who sells made to order kits, and ships overseas, the complete kit new Approx $1000.00
What I found is that if you go back far enough in jaguar forums ( or any other site ), seems as all these new kits need a h-ll of a lot of work to make them fit properly. So I suggest a used kit ( it's already been fitted )
Still Interested ? If so let me know and I'll help best I can.

 

Thanks for the feedback. I'm sorry to say that route is just way too expensive.....

Note- there was indeed a version of the TWR kit that was made for the US models and allowed the rubber bumpers to stick through. The Euro pieces and the aftermarket are not like that....

I'll keep looking.......

 

Found locally in the back yard of a foreclosed house......

The car itself is junk but that's a genuine TWR US market body kit....