Kingfisher has recently started offering a weapons bag from a similar material to the Bujin bags. The Kingfisher version is not quite as beefy, but it is the best I've seen if you can't find a Bujin.
bTw: what iaito did you get and what did you upgrade from and why? Might be in the market myself soon...
Thanks for letting me know, I will go check out their site now
I got my iaito from Budo Aoi. Though their turn around time sucks, the quality of their iaito is top notch. I ordered mine from their in stock list, so it was shipped out immediately. I upgraded from a wooden bokken with wooden saya. I've been trying to save up for one for almost two years and finally bit the bullet and got one.
There are several reputable suppliers out there, and I am sure you will hear tons of various ones. I like Aoi, but a lot of people like tozando and nine circles too. Other people from my dojo have one from swordstore or bugei as well and are pleased.