Found via Maine Gardener: Sweet Pea Gardens. They only sell seeds and books via mail order, but if you’re going to be in the area, they sell lots more than just sweet peas (though that’s a very good start).
I’ve always wanted to grow sweet peas along the chicken fence. I did try one year but they didn’t do much. I think I need to amend the soil significantly before they will do well, and I’ll have to dig all the poet’s narcissus out of that area before I can amend. Yeah, one of these years . . . it’s that kind of a project. This website has a lot of specific cultural information, so, if like me, you’ve had trouble, give this site a read before you give up.