We use Monday.com and really like it. Every week we do a visual inspection of the inventory locker and choose the inventory levels from a drop down menu. This keeps a great audit trail of what was ordered, what ran low, etc. week by week.
If you wanted to integrate this with Jobber and make it more automatic, I think you could easily write a Zap for it. Have your tech add line items such as "Compressor fitting 12XF" and every time that invoice is issued, have the zap reduce your inventory on hand by the correct number. Set automations for low inventory thresholds. I think this is pretty doable for anyone remotely comfortable with software. And you will find a million other ways to use Monday.com and Zapier for operations!