You can also try cfw it performs mostly the same functions as gateway except .3ds filesI have a $100 prepaid visa
Modchipdirect is the one my friend used for himself. He actually ordered mine and a friend's for us since we didn't have visa. He lives in Canada but we live in the US. They ship out of NYC I believe. Very reliable and I got mine in 2 days of order.
Oh you may not be able to use a prepaid visa. You technically pay another country, probably china. Prepaid visa do not go international as far as I remember. A friend had that problem too.
I'd save your money. 9.2 has cfw, and downgrading from higher firmwares seems imminent.