you can buy the 春卷皮 at either citysuper or any Thai grocery shops.
If you want to eat it as cold roll. Dip the 春卷皮 into hot water for 10 to 15 seconds, then take it out and put on a chopping board. You can put any stuffing you want like pork, prawn, rice noodles, herbs, bean sprout etc. The dipping sauce is also very easy to make. Fish sauce, vinegar/lemon juice, cold water, sugar, minced garlic and chilli.