Don't known about Chinese egg noodles in Nijiya Japanese supermarket. They do sell fresh (in the fridge packaged from elsewhere) Japanese soba/ramen. For Chinese lo mein, if not in Nijiya try Lucky Seafood (Mira Mesa) or Ranch 99 instead.
Not sure if Nijiya has them fresh. Possibly frozen. Call them to confirm.
I've never seen them there since this is more a Japanese market. Most of the noodles are either ramen, udon, or soba noodle You might want to check at either one of the 99 ranch stores. Both are more of a Chinese Market. Well I would go to the newer one on Balboa Avenue. Another place you may want to try is Zion market on Clairemont Mesa Blvd. This a korean market. They do have a wide array of noodles.
Thanks! Your answer is awaiting moderation.