I stopped by my local Dollar Tree store yesterday looking for small plastic containers to use as molds for fragrance test batches. I happened to find small silicone loaf molds (278 gm capacity using water; about 1 1/4 cups), 500ml rigid plastic measuring cups (in snazzy colors even!) and very small (about 2" in diameter) mixing bowls with the smallest pouring spout your imagination can handle. They are semi-flexible-the sides squeeze in just a bit. The loaf molds do bow out when filled but I shoe-horned six of them into a box. The bars are a bit wonky due to the flexing but they're just for test bars so I don't care. The loaf molds and measuring cups were $1 each. The bowls came in a set of 4 for $1.