I seem to recall the downgearing is 1/65, you can check the pololu website if they have anything similar (I can only see 50 and 75 so you'll need to choose).

If you really need a different motor you can buy both (they're not expensive, just get the 50 and 75 gear reduction). If you want to spice up your current motor use a 2S Lipo, that'll do wonders for it already.<br type="_moz" />