Does a natural product for incontinence exist?

Depends what U mean. No if you are asking about herbal treatments. There are no herbals that are reliably effective for incontinence. However, there are lots of natural non-medication treatments (kegals, timed voiding, etc) for both stress and urge incontinence.
Not that I know of. There are herbs sold for this purpose but not proven to be effective. If some are, that will be due to their content of a substance that relaxes the bladder. Beware of the opposite i.e. Lazy bladder with difficulty passing urine. Also, if effective, medications are safter bec they were well studied and dosed accurately and their side effects are well known. Better go the already tested route.