Hmmm, are you talking about the brown soba buckwheat noodles?
Try these japanese food sites.
http://www.asianfoodgrocer.com/category/鈥?/a>Question for Japanese people about Japanese cooking?
I am going to recommend a Korean brand - Wang.
One of their dried noodles will give you a taste and texture very similar to soft Chinese hand pulled noodles or Japanese ramen. I've tried A LOT of dried noodles from many Japanese, Chinese and Korean brands. Only Wang managed to produce a taste and texture similar to fresh soft Chinese hand pulled noodles or Japanese ramen! But, stay away from Wang's dried udon noodles; that stuff is pretty close to garbage. Oddly, Wang dried noodles is not that popular among Koreans. I think their taste is too Chinese/too Japanese.
This is one of their dried noodled. This one is dried somen or extra thin noodles: http://www.groceryshopping.stores10.com/鈥?/a>
I can not find the type you're looking for online but they are not that hard to find in Korean grocery stores. H-Mart carry a good selection of them.
This and many other frozen "fresh" noodles will work well too. http://newcentralmarket.com/Gallery1/alb鈥?/a>