Thanks. I didn't find urine as a cleanser, but on this very website, I found fly patterns with urine in the recipee.
The Light Hendrickson and Female Hendrickson call for this:
Body: Urine Stained Belly Fur from a vixen fox. (tanish grayish, pinkish)
Tup's Indespensable is even more interesting:
Body: Mix white fur from a ram's testicle with lemon-coloured fur from a spaniel and cream seal's fur with a small amount of yellow mohair.