Back in the early 90s at the Philadelphia College of Textiles and Science, there was a design class for students who would study a special-needs group of people and create a useful garment for them. One of the designs was a special coat for the homeless, warm, waterproof, no fasteners except a tie belt, and deep pockets.

There were a flurry of articles at the time, but I can't find anything recent. And I couldn't find any photos at all, although from memory of the article in a magazine, it was a form of greatcoat.

Here's the article, a good idea:
Shelter-Pak Coat

Sue