You can order the stuff from
http://www.brewingscience.com./ The CL-50 that Denny recommends is $10 a plate with free shipping, but there is a $30 minumun order. Go directly to the "Order" tab or you will get discouraged by the barrel prices for yeast.
Alternatively, I have had great luck using Wyeast 1272 for Denny's RyePA. This is also Denny's second choice for that beer.
Wayne
Bugeater Brewing Company