Have to check out the yarrow. As for commercial products the Repel Earth Scent has been used by several with success. Castor from beaver works well and yes you can buy it online at www.bugspray.com. According to all the research I have done its one of the things used by the old mountain men/beaver trappers. It has three guarantees:
1. you will not have mosquito problems
2. you will not need a cover scent.
3. you will not have to worry about your love life. you won't have one so don't worry about it.

Hey, size may not matter but it sure IS nice!