I'm not exactly an organic gardener and I found a very cheap, 3 dollar plant food called Gro-Fine Tomato Plant Food.
It claims a NPK of 16-19-29.
But is this brand trustable? Does anyone know? I couldn't find anything about it on google.
The company that makes Gro-Fine, Knox Fertilizer Company, Inc., has been in business for more than 60 years. They must be doing something right. Since you're "not exactly an organic gardener" I think you'd be fine with using it, unless you find something on the lable that gives you the heebiejeebies. The company must be doing something right if they have stayed in business that long.
I hope that helps.
Straight NPK fertilizers are simply mixtures of inorganic chemicals, so I don't consider use of such fertilizers to even be an organic gardening issue.
all you have to do is triple the nitrogen and you will have a very good citrus tree fertilizer