I actually use the pouch I got with my P5 headphones. I think you can get it for like 25 euro's.
It fits perfectly, also with a case around it, and it even has a little extra compartment to put accessories in.
I picked up this STM case from B and H Photo in NYC, adds almost no weight to the Mini, but does snap onto it, so it is hard to remove.
http://www.bhphotovideo.com/c/product/898137-REG/STM_stm_222_023g_01_Skinny_iPad_Mini_Case.html