One of the following three options might fit:

http://www.gotbatteries.com/items.as...SL139/35L139S1
http://www.gotbatteries.com/items.as...SL152/37L152S1
http://www.gotbatteries.com/items.as...SL154/37L154S1

If none of those work, you may be able to assemble a pack from:

http://www.gotbatteries.com/items.as...SL125/35L125S1

which are much larger than the original battery, or perhaps from:

http://www.gotbatteries.com/items.as...SL149/37L149S1

which are the Cyclons that were mentioned earlier.

Sorry for the single-site links. They have a fair price and a good
search engine, so it made my job easier.

-Keith