The Dog Clip is the common name used for the V90124 side retaining clip for the Halkey Roberts Alpha V90000 Inflator.
You can buy individually. There is also a multi pack option on this link.
It has often surprised me how many lifejacket users rarely check inside their jackets. I used to work for a Norwegian company and covered the UK and Ireland. The Alpha inflator was the Norwegian’s chosen inflator in their devices. I used to visit customers and inspect their lifejackets, often finding them without the Dog Clip. These clips can pop out if you lightly snag the toggle without inflating the bladder. Then if the Dog Clip is missing, it is much more likely you will have an accidental inflation as any slight snag of the pull toggle could inflate the bladder. That could be slightly irritating if it happens whilst out on a vessel. It could also be dangerous if it happens when climbing steps at the harbour side.
So please check regularly inside the bladder cover. Whichever inflator you have, it is a good idea to keep a few spare clips handy.
The Alpha Inflator is also referred to as the V90000 and has a black body. The Alpha is a modern inflator and has manual and automatic inflation.
RTS supply individual service parts for the Alpha inflator, as well as re-arming kits.