Strings by Mail has a pretty good selection at reasonable prices (though sadly, not my JF365s, have to ask them about that). Shipping is $4, assuming we're all in the US.
I just found this place earlier this week, when I was looking for some different classical guitar strings to try. They had an amazing selection, and I got some really helpful advice over the phone in narrowing it down. Just for grins, one set I'm trying is TI KR116 - all rope core, with flatwound basses and nylon tape wound trebles - should be interesting.