a friend of mine told me about this and i tried it on my honda it worked great:
go to home depot in the caulking section..they have polyeurathane chimney sealant, or roofing sealant or whatever as long as it is polyeurathane(which is the same stuff that the mount inserts are made of) they cost about $3.95 a tube. one tube will fill most/all of your mounts. just get a caulking gun and fill em up, turn em over, fill in any holes and let it dry for 24 hours. and blam now you have brand new polyeurathane motor mounts. for less than $10