Hi , Prasad,
If you replicate materials to SRM - you do need catalog for them. You can just order internal material with material number. No catalog features such as MDM or OCI are used. When user creates shopping cart he should order internal materials or services - additional link on the screen, where catalogs are shown.
As for vendors - you need to replicate them - then you can use them in SRM on a position tab "Source of Supply".
Best Regards
Konstantin