Where are you located in Wisconsin? If you are near the Southern border, Red Buffalo Nursery, in Hebron, sells native plants and has milkweed. http://redbuffalonursery.com/plants.php
I do not think he ships. He's into native restoration on his own property.
Prairie Moon Nursery is from where I also get my seeds and plants. http://www.prairiemoon.com/
They ship and have a gigantic selection.
Both are very helpful with questions.
I've never asked if they both use pesticides but presume not. Most native plant specialty places probably don't as they need insects to make the seeds they need to sell. I would think they normally welcome insects. Both places have their own land from which they grow plants to make seeds to sell. I pretty sure both would have to use herbicide to control the invasives taking over their fields.
Being involved with restoration with our own and, I've found that judicious use of herbicide is necessary. There's no way to control things like reed canary grass without it, unfortunately. I hand wick each blade of the reed canary grass to diminish run off and spraying things that don't need to be sprayed. It significantly reduces the amount of herbicide used and is on only the target species. I wish I didn't have to use any but that grass spreads by runners (I read 12 feet a year) and obliterates all natives in it's path. It's the worst I have encountered and this year it just won't die. I had to hire someone else to redo the site as my Spring work (about 12 hours time) had the grass laughing at me. It was 7 feet tall weeks after I wicked it. I had to brush cut it to the ground and remove the debris in weed bags. That took another 6 hours. I'm not sure if you're involved in restoration so, if not, it's just an example of why it's needed. I still don't know if their work is going to be effective as they just finished wicking. I have to have them do it again late Summer, early Fall, as that is the most effective time to get the plant to uptake the herbicide into it's root system to kill the runners.
My land is in between Harvard and Alden. If you're around there and you need seed, let me know and I can hook you up. Just let me know what type and I can check around to see who has it. There's a bunch of people there doing land restoration.
I hope this helps. If you need anything different than above, let me know and I'll see if I can help or no someone who can. I'm excited about your garden. It sounds so nice.