Those are LLW type of guards, as seen here:
http://the.shadock.free.fr/sherman_minutia/manufacturer/m4a1_lima.html
I don't know of any aftermarket in this style, but make sure the tank you are modeling is a Lima tank before expending too much effort on acquiring some.
For chain I have loosely twisted two strands of fine armature wire together and cut lengths as needed.
KL