This is probably one of the easiest things to switch out. If you don’t have a blender, use your hands! You simply need to use a jar or a container that has a lid. Some options here include a mason jar, a piece of tupperware, a cocktail shaker, and a blender bottle (maybe you had a blender and the base broke, but you have the bottle and the lid). The best-recommended piece is the cocktail shaker, since they are meant to be shaken, not stirred.
Once you have the milk, cream, ice cream, etc. in the container, snap the lid on and make sure it’s on good. If it’s not on good, you may spill it everywhere. Then, grab it by the top and the bottom, and shake it up and down.