Try Zodiac products.

I use their flea shampoo on occasion as well as Frontline PLUS (regular Frontline does not work for us.) I only bathe them with Zodiac on occasion. Between those baths they get baths with Tropiclean Neem.

Honestly, the only way we are able to keep fleas at bay are bathes weekly - every 2 weeks, vacuuming daily, spraying the yard often, and making sure to put monthly Frontline PLUS on them.