Am trying to work on this topic 'effect of pH, temperature and metal salts on the stability and activity of alpha amylase produced from Rhizomucor pusllus'. Just need a carbon source for the production.
Have you considered starch, seeing that this is the substrate for alpha amylase? Alternatively, a number of commercial kits are available which use a colorimetric assay (e.g. http://www.biovision.com/amylase-activity-colorimetric-assay-kit-3732.html).
You can use different type of starchy carbon substrates such as corn starch, potato starch, soluble starch, tapioca starch etc in case your enzyme is an inducible enzyme. But if your strain secretes constitutive enzyme you can use any simple carbon source such as glucose, sucrose, maltose etc.
You can use the tubers or cereals mentioned above. These you can prepare yourself. You can also use the wastes (chaff or peel) from the processing of any of these starches as your source of carbon. I have attached an article which I believe will be of help.