Dry Kool Bloom, while it is salt it is suoer effective with cukes, tomatoes and peppers, the mainstays of our garden. A little bit does the trick too, so I don't sweat using it in the garden which doesn't get salt nutes usually. I grow pot organically and do not use it indoors or out. I have not used a specific organic bloom booster, as far as I know.
I used Epsom Salts & molasses for years. Worked great. Am trying out Dr. Earth Organic Flower Girl. Package says Bud & Bloom Booster. Also some stuff from Kelp4Less, Ripe Bloom. K4L has a lot of organic 'helpers' for Mary. Last 2 years, so far so good.
I recently switched to their liquid form of shooting powder for just that reason. It doesn't seem to make the PH jump through the roof like the powder does.