Is there a replacement for the discontinued AVC-P plastic bottle type, shallow well air volume control?
Yes, we do offer alternatives to the discontinued part no. AVC-P plastic bottle type, shallow well air volume control. Zinc plated metal air volume controls with a spring loaded diaphragm are available in two sizes.

Boshart Part #: AVC45
AIR CONTROL AVC45 – Use on hydropneumatic tanks up to 42 gallons.
Boshart Part #: AVC100
AIR CONTROL AVC100 - Use on hydropneumatic tanks up to 120 gallons.
For information on how they work see this article:
https://support.boshart.com/shallow-well-air-volume-controls