Has anyone used any of the Exopdisc alternatives such as the ExpoCap or similar generic white balance lens cap? Another alternative I've seen is called ExpoAmigo and is a 120mm x 100mm sheet of what looks to be the same material as a normal Expodisc. Has anyone tried any of these? The ExpoAmigo is $10 + SH on ebay... generic ExpoCaps go for as low as $5 on ebay... Anyone try any of these?