I have never seen anything like that (US MK3's). For the head unit, I have a half pocket and then a single DIN CD (Eclipse). Right now, I am mounting my Apex-i AFC in the top pockect above the CD player. I prefer the single DIN because of the extra space you get. I've seen turbo timers as well as boost controllers mounted in the extra space.
You may want to check out www.supraforums.com and look into the MK3 section for more info. Right now we have about 550 mk3 owners in that section.
If you're looking for any US parts, I should be able you hook you up.