A written reminder, placed where you'll find it at the right time, is a gift from yourself.
"If you can see this sign, it's time to reorder this item" is a great way to manage inventory in-person. This can be a printed sign with detail about part number and supplier, or a scribble of marker at the appropriate low-level mark on a jug of oil.
Online and digital inventory systems are useful too, but some days you are spending all your time on the floor. Physical reminders work well for a physical production space.