Those are called E-clips.  Take one into any decent hardware store and you should be able to find one.
I have this kit because I've launched or broken so many of them: http://www.harborfreight.com/300-piece-e-clip-assortment-67653.html 

Stuart

From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of Steven Johnson
Sent: Thursday, July 23, 2015 8:41 AM
To: vanagon@GERRY.VANAGON.COM
Subject: It's the annoying little things...

Hello All,

On my 90/91 Westy I was replacing the shocks/struts for the rear hatch and while doing so launched into oblivion one of the little circlips that hold the one open end on.

Does anyone know the correct size and metallurgy for these little guys so I can maybe
pick one or two out from the hardware store?   Or these specific only to
that particular
connecting point?

Thanks!

Steven

91 Westy