How much area do you need? I used to use this company - they will supply Sterling silver cut to your dimensions, .5mm thick, for 80p per sq cm
http://www.kernowcraft.com/products/metal/metal-sheet/sterling-silver-sheet-A83/
Sterling Silver is considerably cheaper than 'proper' silver but shines up very nicely.
http://www.kernowcraft.com/products/metal/metal-sheet/sterling-silver-sheet-A83/
Sterling Silver is considerably cheaper than 'proper' silver but shines up very nicely.