Camelbak Chem-Bio Hydration Reservoir System. Pictured with Standard Bite Valve, Type M (MSA), Type A (Avon), and Type S (Scott) Gas Mask Drinking Tube Adapters. : r/gasmasks
CamelBak with this Type A Adapter has made it easy to attach a chemically resistant reservoir to your protective gas mask.
Camelbak HydroLink Type M Gas Mask Adapter - 2 Pack - Military Stripes