We have this barrier.  It will fit behind the back seat of a vanagon, but not behind the drivers seats.  There are other ones out there that might work better.
I would urge you to check your area Craigslist, as folks sell these often.

> Date: Wed, 28 Nov 2012 11:24:52 -0500
> From: magikvw@GMAIL.COM
> Subject: Re: Pet Barrier
> To: vanagon@GERRY.VANAGON.COM
> 
> Here you go:
> 
> http://www.gowesty.com/ec_view_details.php?id=3362&category_id=&category_parent_id
> =
> 
> 
> --
> Thanks,
> 
> Jeff
> '85 GL (Gertie)
> '78 Bus (Melissa) Patty's Bus