YesAsia is usually pretty good. Their prices can be a little steep, imo, but I'm not sure how much this stuff usually goes for. If you wanted to find it cheaper, you could check eBay or maybe Amazon, but I wouldn't pay anything higher than a price on a site like YA. Otherwise, you're probably being ripped off.
[edit] and lets not forget all the people here on AHS in the Fan-Sites section who are selling their Ayu merchandise.
At the same time, I'd say that AHS (and eBay or Amazon) is more at-your-own-risk than YesAsia or an actual retail/import site.