On a recent visit we were turned off by the high prices at Mitsuwa (River Road in NJ), comparing them unfavorably with those of similar Japanese items sold in Chinatown and at Sam Bok in midtown Manhattan (maybe prices are better even at Sunrise Mart in NYC, but we've never been).
We've had terrific success at the Han Ah Reum shopping center (off 1/9 near the GWB--anyone have a better address, I hope?). Obviously you can't find every item you might want there, but we found shopping for all make-your-own-sushi items easy and cheap at Han ah Reum (and why do my chowhound searches come up with zilch on this place? There must be posts!) We also like their 1/2-price sushi/sweets deal near closing time.