McMaster Carr also sells a locking gas spring.  Perhaps a better alternative since you won't always have bikes on the rack.  Scroll down: http://www.mcmaster.com/#gas-springs/=k93iuv 

Stuart

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of Harry Hoffman
Sent: Tuesday, November 20, 2012 3:46 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Rear hatch struts - heavy duty

Hi All,
Bus Depot offers a set of heavy duty rear struts. They supposedly can hold open the hatch even with a bike rack and bikes.
Unfortunately they are on back order for 2-3 months.
 Anyone know a alternate vendor?

Cheers,
 Harry