Head to your local thrift store, or even your closet, to acquire several wool sweaters for making your own wool cloth diaper covers. Choose sweaters that are 100% wool (or very nearly so), free of small holes, and soft (not itchy) to the touch. One wool sweater will generally make one pair of wool longies or shorties, plus one to two pull-up style diaper covers.
Next, wash the sweaters in the washing machine in hot water to felt the wool. You want the wool to be thick and shrunken so it will contain moisture. Use a small amount of a gentle, unscented detergent. Dry the sweaters on high in your dryer. You may want to repeat this process until the wool is properly felted.
Once you have a shrunken, felted, soft-feeling sweater, you are ready to do some basic sewing to turn your sweaters into diaper covers. Wool makes a great diaper cover because it is inherently anti-bacterial, breathable, and highly water resistant. The natural lanolin found in wool fibers acts as a water repellent. Periodically, you will need to re-lanolize your wool covers to keep them effective at retaining moisture. Follow this tutorial on how to lanolize wool covers.