Viagra is viagra. If there was an equilivant herbal form, they'd have found it years ago and patented it.
Ask your doctor when you're in for your yearly checkup. Better yet, just call them. When I went in for some joint pain in my shoulder, they gave me free samples of Vioxx, right next to it in the sample cabinet was a bunch of Viagra.
The "online pharmacys" are shady at best. There are SOME legit ones that bring drugs in from canada (mostly geared towards seniors), but they probably don't have viagra. If you get scammed, there's no recourse, because they're not government mandated or FDA controlled.