I took a stock quarq Cadence magnet for threaded bottom brackets and mounted it on my Spark 900 with PF GXP BB

Took a scribe and made a 42 mm circle on the existing and dremeled a bigger hole re-pressed the cup and voila cadence magnet.

Quarq Magnet for Scott Spark 900  +  PF GXP BB-2013-05-31-11.59.52.jpg