Gandhi may not sell dhal puri since it is not a West Indian roti shop. Dhal puri is used in West Indian cooking and is totally different to East Indian roti which does not contain lentils. That being said, maybe try calling a West Indian grocery store in your area to ask?
I know someone who makes the best dahl puri in Toronto than any shop in town. Minimum of 20 purchase required though. Ideal for small gatherings or larger. Let me know if you ever come back to this post.