There are Canadian pharmacies that offer much better pricing, but be careful - some of them are selling look-alike drugs from India, etc., and some of those are not effective. The legitimate ones require you to submit a prescription - any that say they’ll sell you the meds w/ out Rx should prbly not be trusted. Although your Dr. doesn’t know, some Dr’s DO have info on legit Canadian pharmacies, so ask around...
I agree with caregiver222 that buying online has risks associated with it due to not being well regulated. These days, there are apps that do local searches (in the US) for best pricing at a local pharmacy. Saves a lot of money and the better way to go.
There is no best "on-line" place. The internet is unregulated and you are never sure you are getting the actual product. Some of the best prices in the U.S. are at Wal-Mart in store.
Can you list a specific herbal product that is good?