ONT- I'm sorry, reading comprehension must have escaped me on this.
1] the dimensions I originally posted are cut/pasted from your post above.
kindms was able to contact Eco Charge for a recommendation as he mentions in his post- but here is what I found about the BP 50:http://www.ecocharge.com/batteries_bp50.html
• 6 volt, 7.2 amp hour
• Dual output XLR connectors
• Auto short circuit protection
• Max. current draw: 3.0 A @ 50º C
• Dimensions: 6 x 1.4 x 5
So the battery you found seems to be close except for height- it may work! and is strikes me Eco Charge's height measurement includes their top, so it is real close.
Hopefully someone else can help to confirm, but I would say you may have found one that works!
I just checked greenones thread, you have found the exact one he used! http://taperssection.com/index.php?topic=119878.0