Essential oils can be purchased at organic or health food stores for about $5.00 - $8.00 US. 1 fluid ounce is usually sufficient unless there is a bad bug problem.
Non-toxic and/or biodegradeable soaps can be purchased at organic or health food stores, and many major grocery stores now carry such products. The cost for these soaps varies, and at some stores, soaps can be purchased in small amounts as bulk.