Osmocote Pure & Simple

Dumme said it right. I just wanted to add:

In general (and I hope agricultural companies respect this established order) NPK should mean percent of each substance in the bottle you buy.

So 14:14:14 could be read as 14% of Nitrogen, 14% of Potassium and 14% of Phosphorus in fertilizer bottle (~ 140 ml of Nitrogen in 1 liter bottle). By diluting with water you get solution you need (it is better to measure EC specifically in hydroponics).

If you buy 1:1:1 you just need to add more of it to get same solution strength.

Mineral fertilizers are easier to produce with higher NPK (its values can reach double digits) on the other side organic fertilizers are usually very mild (max. single digits) in NPK. See comparison here

When shopping you can then compare different brands and its NPK (amount of pure NPK) to its price.