If you have friends or family that have stayed at hotels and took those little bottles of shampoo, conditioner, and soap home with them and are just stuck in a drawer somewhere in their house. Ask them for it and store it. Duh Hubs and I have family and a couple of friends that travel for their jobs and had a ton of that stuff hanging around. I asked them for it and have it in my storage in a couple of small totes. I think we have enough to keep clean for at least a year. LOL It's free and you'd be doing them a favor getting rid of it for them.
Oh forgot, check out the Goodwill and thrift stores. Someone donated a bunch of that stuff to mine and for a couple of dollars I got it all and added to the preps.