We do a kit that uses the Boxster bottle. Comes with everything you need. Even doubles up the fuel light as a low fluid warning.

https://www.classicretrofit.com/collections/other-parts/products/911-washer-bottle-kit

I'm coincidentally looking at the exact same project right now. Here are some pics from my '87, and the intensive bottle.

Bottle peg 1 fits into the square fender hole 1 and seats well. That then aligns horizontal bottle hole 2 with round hole 2 on the fender.

What's odd is that bottle hole 2 is way smaller than hole 2 on the fender, so not actually sure how it's supposed to attach there. Screw into a grommet of some sort?

There's nothing in the PET I could find that notes bolt/screw size, or any other fastener for this. I could see how a ziptie here would work, but that seems like lunacy. ;)

http://forums.pelicanparts.com/uploa...1657318514.jpg
http://forums.pelicanparts.com/uploa...1657318514.jpg

It uses a spring clip, don't remember if it's the same size clips as those used for the front fenders though.

Aha! I can totally see how that would work now. Thanks Arlo!