at a bike shop. Ours actually has a huge selection of seats just for women, and you can bet I got the widest, softest bike seat I could find, but I shelled out $70 for it too. I think he said the top layer of padding was that tempurpedic material, which is nice because it molds and supports. LoL. Seriously, I can ride all day. My legs would get tired long before I got sore.
The stock double spring wide seat that came with my Micargi was okay, but I have really long legs, so my seat HAS to be high and it dug into my crotch when I leaned forward to pedal faster. Some women it doesn't seem to bother no matter what kind of seat they have, but I have serious issues with my girl 'down there' going numb, losing my panties to my butt crack, and rolling around town with camel toe. I'll take my grandma bike seat any day. It's not aerodynamic, but then i'm not trying to get anywhere in a hurry anyway.
Try the gel seat and make sure you get a nice wide one. You'll love your bike once you've got something comfy to sit on.