I was and am so excited by Joseph Lofthouse's work that I sent him probably my biggest seed order ever last winter.
The local seed movement has spawned a local seed co-op here called triple divide. They don't sell much online yet- but you should look for your most local co-op or small seed company.
The local seed library.
The local farmer's market- I bought three squash, some beans, two tomato plants, and some popcorn all with the intent to save seed last year!
Sandhill Preservation Center
Online trading partners- I got some amazing things swapping seeds online last winter.
Backyard Beans and Grains / Resilient Seeds
Seed Racks especially from certain companies like triple divide seed co-op and irish eyes garden seeds- which still carries some of the old Garden City Seeds varieties a company they purchased.
The bulk bins at my organic grocery- especially when the seed has a sticker that says "local" or "Grown in Montana"
Family sometimes gifts me seed. I plant it and try it out.
The most important source though? The tried and true, seed saving from my own garden. Quantity matters and so does seed quality. If I save my own I control both. Also I can save and replant seeds from vegetables I've tasted. I planted all the seeds out of a Hidatsa squash I grew last year that was allowed to open pollinate. Now I have dozens and dozens of its offspring Hidatsa squash crossed with Rio Lucio a squash I've grown since about 2000. The cross is fun and it tastes good. Next year's F2 will be fun. What's more I know I like it. If I had grown only Joseph's squash I would only have 1/3 of the squash I have now? Why? Joseph sent generous seed packets, but there are a lot more seeds in a squash than in a seed packet or 3 or 4 seed packets! I have numerous Lofthouse squash on my seed saving pile. I've eaten one so far- a Lofthouse buttercup. Definitely planting a lot of it next year- and I will be able to because I saved the seed myself! Note: more important than Joseph's seed is his ideas!
Western Montana gardener and botanist in zone 6a according to 2012 zone update.
Gardening on lakebed sediments with 7 inch silty clay loam topsoil, 7 inch clay accumulation layer underneath, have added sand in places.
I know it's a big company but baker creek is good good germination good sized packets. I don't like pityful seed portions that means I son't really like strictly medicinals and bountiful gardens. Hudson, terrible outdated webiste but good germination. I look at garden watchdog ratings.