Hi Rutger,
Back in 2011, Rafael Meneses sold me most of a vent grill (one or two slats missing) to use as parts to fix a broken pot metal actuator frame in mine. I still have most of it, somewhere in my garage. I don't know if I have the grill slat that you need but if I do, I can ship it to you for the cost of postage (free + postage). I looked a few minutes ago but didn't find it. I've seen it not too long ago, but it's going to be hard to find mixed in with all the other parts that I have to put back on the car. I'll look again tonight and tomorrow and if I find the little box of pieces, I'll photograph what I have, you can tell me which slat it is (they are all different lengths) and I'll ship it to you from Eastern Canada. I can sandwich it between two pieces of cardboard and ship it as a letter, I think.
I'll get back to you as soon as I find it, if you are interested.
Tom Kizer