I bought one of these and soldered on a connector cut from a magicshine extension cable:
http://www.all-battery.com/li-ion186...bareleads.aspx

It's $72, sorry. I bought mine when they were on sale for something like $28 a year ago. Given that it's twice as big as the pack MS charges $45 or so for, it's actually not a bad deal.

For about the same price, there's this:
http://www.all-battery.com/Li-Ion186...BearLeads.aspx
or this:
http://www.all-battery.com/flatli-io...onnectors.aspx

The shape is different but it's got decent capacity.