Fellow 128-ers I want to share with you that I sourced a Euro box from Sweeden for about 250 total. Cant wait to get it. I still need to get a filter thinking using afe pro dry in euro spec.
Used their version of car-part.com here:
http://en.bildelsbasen.se/
and google translate
Contact them using their yard home pages and email links. The Inquiry button is almost like a Buy button, so be careful.
Shipping for items is in the range of 700 - 1600 SEK or 100-250 USD so contact multiple vendors.
From my searches, the website has exhaust manifolds, m3 parts, intake manifolds and air boxes. Just make sure the shipping justifies a used part.