You can contact the various commerce chambers in India. For example, in Pune, the list of all SMEs is available with Maharattha Chambers of Commerce, Industries and Agfriculture (MCCIA). They provide the list in CD form.
Similarly you can get the list from different commerce chambers across India.
A few are given here dealing in Al casting side e.g. shanti engineering works, Ludhiana-good SME, another Quick Engg. working on Al&Steel located at Govindpura, Bhopal.