A few dealers used to put their logos/crest on them back in the day - Rusnak Pasadena CA comes to mind (see smg914/Steve G's Sahara Beige beauty in the O&H Forum's "The few, the rare..." nailed thread).
But today you'll need to make them up with the domed Porsche Crest decals & some billet aluminum repro caps (or black plastic center caps) available in TheSamba.com classified ads.
Given the high price of the reissued aluminum center caps now sold by Porsche (Classics), I wouldn't put the decals on those.
PS - Those modern decals will deteriorate in the sun after a year or two or so, so keep the car covered, &/or buy an extra spare set of decals.
Tom
///////