I would be VERY wary of using any oils or creams on a sporran. The big danger here is that they may stain the kilt (and you might NOT get the stains out), or at worst, damage the fabric of the kilt. You can hasten the 'weathering' of the leather by manipulating by hand, just gently keep bending the leather back and forth, and it will eventually crease a little and look 'worn in'. You can do this while you're watching TV.
Better let 'nature' take it's course....