I really like International food market on Rt. 9 in Hadley. Really nice Cambodian couple own it, and they get some fresh ready to eat Asian and Indian food from NYC (samosas, dumplings, curries, yum). Plus it's right around the corner from mi tierra! :)
Not sure about Springfield, but there's Tran's World Market in Hadley. Don't know if they specifically have tofu skin, but you could call and ask.
Also, check this out:
Someone else posted it on another pioneer valley thread a while back.