Make compost, leaves mixed with grass clippings, etc.. You could even compost wild caught fish scraps. Make a leachate from wild plants or "weeds", the link below talks about this subject. Find "free range" pastures for manure.. Wood ash in very tiny amounts for trace nutrients, also kelp and azomite is good for that. The possibilities are endless.. You can even use diluted urine..

Here is a link that might be useful: Plant leachate

For many of us organic growers the term "organic fertilizer" is an oxymoron since we think more in terms of building soil health with compost and other forms of organic matter instead of using something that may not truly feed the soil that feeds the plants. Other than compost, cover crops, shredded leaves, and other vegetative waste what your soil may need can only be determined by a good reliable soil test.
Few animal manures, today, will be free of GMO byproducts since most all animal feeds use grains grown using GMO seeds, unless one can find an organic animal raising operation with enough manure to sell.
The Bacillus thuringiensis bacterium is a naturally occurring bacterium and you most likely already have some in the soil where you are, just not enough to be a very reliable insect pest control. The problem with the BT bacterium is what happens when we ingest them, since no research has been done we have no idea.