I bought mine from BumperPlugs for $24.95
I think if you have a white, red, or yellow Boxster it is worth the $$$ since it is an exact color match and very hard to tell they are installed.
Part number 999-703-432-40 does not look like it would be flush with the bumper :
https://techinfo.porsche.com/techinfo/pdf/de/catalogues/D_986_KATALOG.pdf
Page 216 Item 2
http://www.********************************************.com/model/986catalog/986-2.pdf
Page 98 Item 16 & 21
Page 99 Item 2 & 10
Norm, do you have a picture ?
Thanks,
Nick