What ending do I need to attach to plug into CMOS?

I was thinking about using one of these as a CMOS battery for my Galilao:

http://www.amazon.com/gp/product/B005J1UC30/ref=oh_details_o05_s00_i00?ie=UTF8&psc=1

The ending that plugs into the Galilao is too small.

What ending do I need to buy?

Is this not a good idea?

If not what is a good alternative.

Thanks!

supsup