Breed your own seeds that are perfectly suited to where you live. All you need do is select seeds from the most healthy and productive open-pollinated (not hybrid) plants you grow, save the seeds, and replant them next year. Select seeds again from the best plants, dry them, and repeat the process. Within four to five years you will be growing from seed that has been naturally selected to thrive in your microclimate, your soil, with your pest and diseases, your rainfull, and so forth. The longer you do this, the better it gets.
You can select for whatever characteristics you want, but always select from the most healthy and vigorous plants. For tomatoes, for example, you can select for earliness, productivity, resistance to disease, whatever you like. The result after a few years will still be the same variety you began with, but just a little different, and it’s all yours.
In the days when everybody had a farm or vegetable garden, before mailorder seed houses, seeds were saved and naturally selected in just this way – which is one major reason that their gardens thrived with virtually none of the disease and pest remedies we have today.
Of course they all (ahem) grew organically as well.