https://flowerpowerfertilizers.com/en/feeding-schedule
tough, slow working with emails and the Netherlands, seems a scale that weighs in grams, or a gram and less is needed and working with liters, 4 liters make 1 gallon
Here is a conversion chart and the conversion factors:
EC Hanna Eutech Truncheon CF
ms/cm 0.5 (x 500) 0.64 (x 640) 0.70 (x 700) x10
0.1 50 ppm 64 ppm 70 ppm 1
0.2 100 ppm 128 ppm 140 ppm 2
0.3 150 ppm 192 ppm 210 ppm 3
0.4 200 ppm 256 ppm 280 ppm 4
0.5 250 ppm 320 ppm 350 ppm 5
0.6 300 ppm 384 ppm 420 ppm 6
0.7 350 ppm 448 ppm …
Amazon has a few scales, $9+, just an example
https://www.amazon.com/American-Weigh-Digital-Scale-sensitivity/dp/B0012LOQUQ/ref=sr_1_3?ie=UTF8&qid=1483994662&sr=8-3&keywords=Gram+scale#Ask