Great for beginners on a budget:
https://www.amazon.com/General-Hydroponics-pH-Control-Kit/dp/B000BNKWZY/ref=sr_1_5?crid=3O0LOMTVFRO8O&dchild=1&keywords=gh+ph+up+and+down&qid=1624652148&sprefix=GH+ph%2Caps%2C178&sr=8-5?tag=ilovegrowingm-20
dead link
Thanks, and fixed.