The Curved Side retaining green clip is for the United Moulders Compact Manual Inflator.
The UMS1622/1 Curved Side retaining clip can also be bought in a multi pack of 10 or 20 on this link.
It is easy to lose a retaining clip from an inflator by a light snag of the pull toggle. Check your lifejacket regularly. If your retaining clip is missing check the cylinder before you replace.
UML Compact Manual uses the curved side retaining clip
The Mini Manual lifejacket inflator is a small, strong and lightweight product used in both commercial and leisure applications. A benefit is trouble free maintenance. The unit is manually activated with the minimum pull force required to initiate lifejacket inflation. This product is also approved in accordance with the ISO12402 Part 7 standard requirements for lifejackets.