>Andrew,
>Here's a photo of the part, part # 025 121 438  stolen from Ken's web site.
>As you can see it looks pretty simple but one of the inlet/outlets is
>partially blocked internally and has a opening of about 1/4 of an inch.  I
>still think it could be fabricated but I don't have those skills.

That looks easy enough to fabricate. The restrictor should be no
problem either, provided it is WELDED in securely (if it comes loose
and gets into the waterpump there could be hell to pay!). Aluminum so
as not to set up electrochemical reactions, as copper would do.

4 pieces of thickwalled aluminum tube of the correct ID, turned down
to make the flanges, then trimmed and welded in more-or-less the
right angles (I'm sure this is not critical) and the restrictor
welded in and you are set for life!

Any engineering outfit should be able to turn this out at a
reasonable price... probably cheaper than the new genuine plastic
article.

Regards
Andrew