It is funny to me the idea of using a fertilizer low in available N because it you misuse it it can kill. My wife’s mother used to be terrified of sharp knives for the same reason. To me the better the tool, when used properly, the better the tool (as long as instructions are clear enough for an idiot like me to follow).
I only use synthetic fertilizer when I’m starting tomatoes in potting mix - Miracle Gro (the same formula as Richard) because it’s widely available and contains micros and macros (and it comes with a measuring spoon). I don’t want slow release for my tomatoes when I put them in the soil because the idea is to establish them and then have them fruit- not to be excessively vegetative. Anyway, I give them compost I make and mulch them with something somewhat nutritious like spoiled hay so the only addition needed is some N. In spring to very early summer I boost their growth with my own urine (also high in K, which they don’t really need more of than what’s already there). Fish fertilizer would be a good (and often as foul smelling) of an organic alternative because it is relatively quick. So is dried blood (which can burn plants when mixed with the soil).
For those that want precision and have pretty weak soil, I’d recommend an Osmocote 3-4 month formula of time release fertilizer that contains micros- hard to burn roots with that and it releases N in all temps. https://www.amazon.com/Osmocote-Vegetable-Smart-Release-8-Pound-Fertilizer/dp/B00GTDGJ5C
However, in the NE, usually when tomatoes need a boost it is because the soil is too cool for them and no fertilizer will pick them up. Take the temp of the soil before planting. Black plastic on top of the soil can speed to process towards suitably warm soil.