Look at master rigger Allen Silver's web site for a small parachute
accessory called a SMAK pack which holds a hook knive, mirror, fire
starter and a whistle. $45. The hook knife is on a landyard so it
doesn't get away from you at a critical or inopportune moment. The
whole shebang is small and snaps to a part of the harness.

http://silverparachutesales.com/wst_page12.html