A few years ago I bought a couple W0133-1856853-FEB for $12 ea shipped. They are $25 ea now. The packaging they were in had the Porsche part number ending with the .04
This URO part costs under $2. They are a little different though. I love my Boxsters more that $2. If you'd like to give it a try please report back with the review.
"URO 443121321"
Just be sure to carry a few gallons of distilled water.