That tank is 6" diameter by 22" long and about 60% the capacity of the westy tank.  It seems like a good size if you can either convert it to horizontal use. Or just set it upright when you use it.  It would fit in a couple good spots inside a westy.
http://www.amazon.com/dp/B004FPZABK/ref=asc_df_B004FPZABK1871320?smid=ATVPDKIKX0DER&tag=nextagus0019627-20&linkCode=asn&creative=395093&creativeASIN=B004FPZABK

I have to admit those 1lb refillables are pretty cool.  This is what I found for info.  The first run was 5000 units, so maybe they sold out.
 
  
"To find companies that stock propane conversion kits and/or perform propane mower conversions, contact Lesley Shorter, marketing manager of Manchester Tank at (615) 370-6107. Also try your state’s Propane Gas Association for a list of association web sites, or use the Propane Education & Research Council’s “Find a Propane Retailer” tool on its web site at www.usepropane.com. 
http://www.allpropanemowers.com/v.php?pg=232  " 
 
And here is a horizontal 10lber 10.3" high but I don't think it is any better than the verticle 1 gal one I have.
http://www.propanemall.com/productinfo.aspx?productid=9059TC-1 
  
From: Karl <tdiguru@WESTYVENTURES.COM>
Subject: Re: So let's talk about carrying green 1 LB Coleman cylinders
To: vanagon@GERRY.VANAGON.COM
Date: Wednesday, May 2, 2012, 10:46 AM

That tank can only be vertical. I need small and short vertical (<10"),
or short and small horizontal. I won't put propane indoors for constant
camping use.