You know dude, I had to spend a couple hours on the phone to find a big ag supply place that stocked 50 lb bags of salts. And then drive a little over 100 miles to get the salts. But it is absolutely worth it. I can make base nutes of any ratio, I can make homemade hammerhead with the true 0-9-18 ratio (now hammerhead is 2-4-10 or some shit, who wants extra N in last 2 weeks of feeding?).
I spent 181.06 on 5 50 lb bags of salts and a 3 lb bag of micro mix. It has already saved me hundreds of dollars on nutes.
Hope this helps.
Edit- In a pinch, you could always order the MKP and K sulfate online. You will pay way more per pound, and pay shipping costs as well.
I think the old hammerhead probably did well @2.5 ml/gal. Then they changed it to 0-4-8, and lied about "oh it's just a labeling issue, there is the same amount of P and K" and then reformulated it one more time to a more stupid ratio.
That being said, I did the equivalent of 5 ml/gal old hammerhead, and the max listed dosing on the
MOAB container(but w/big specimens) and it worked out well.