I read about these... http://www.cripplebush.net/index.htm The look good and someone mentioned in a thread somewhere...they would work in N scale. You could email em and ask ;-)
Here is another option for you. Bragdon's Geodesic Foam: http://images.search.yahoo.com/sear...dv_prop=image&fr=sfp&va=Bragdon+geodesic+Foam Three layouts in the Bear Valley have used this system with a great deal of ease and satisfaction. To answer your question Yes. A limited supply made specifically for N Scale. Something to think about Rocks and Rock Molds know no scale. It's what feels right and looks good to the eye.
They work in Z scale, too. Rock is not scale-specific. Someone who markets rock for a particular scale either wants to profit from that specific market segment, or doesn't understand scenery. This is a scene on a Z scale layout that uses the Cripplebush rubber rock:
Yup...what I meant was... the cripplebush rocks are not plaster molds...but rubber rocks. That fact and that they can be 'curved' and trimmed to fit N scale layouts and look good doing it is great.