Q. Where can I buy alpines/rock garden plants in Philadelphia area?
There are many good nurseries in the Phildelphia are that sell these. PHS Meadowbrook Farm in Abington will certainly be able to help you.
The North American Rock Gardening Society has an active local Delaware Valley chapter and the members are eager to share their expertise. You will see their exhibit at the Philadelphia Flower Show in the education section of the floor.