I have just been made aware of the availability of a range of 12V Lithium Polymer Battery packs at http://www.tracerpower.com/battery-packs.html
Stewart G0LGS
In reply to G0LGS:
£90 is bit steep! The blurb states a flat discharge profile so they contain an onboard regulator (probably a buck-boost circuit) of unknown RF emissions.
You buy one Stewart and tell us whether it’s a lemon or not! 
Andy
MM0FMF
In reply to MM0FMF:
Reminds me; whatever happened to this marvel?
http://www.sotawatch.org/reflector.php?topic=3829#30635
73
Richard
G3CWI
nice but way to expensive. I use Lipos from the local Heli-Store 3300 mAh at € 30.- After 7 summits I’m very satisfied, the only drawback is that you have to buy a special charger which ist nit cheap. In my case another € 50.-
Take a look at Weightwatching tut Not | DJ3CQ
, unfortunately in German but I think you will understand most of the text.
72, Jo (dj3cq)
The cheapest LiPos I know are sold by Hobbyking. I am working with this one
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=9804
for six months now and I am very satisfied with it. (Thanks to DM5CQ for the hint.)
I use this charger for it:
http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=5548
73 de Michael, DB7MM
In reply to G0LGS:
This pack fits and works perfectly inside the battery bay of an Yaesu FT-817, just put the right connectors on the leads from the rig:
73,
Tom, N2YTF