hi ive got mace mini blizzard just wanted to know if can buy bigger plate and heat exchanger for under supercharger?

You can. There are two available options based on your requirements. One would be to stack another mini blizzard intercooler plate assembly on top of the one you currently have (part number WAI601-A1) or, as you've suggested, replace it with larger plate from our intermediate blizzard kit (part number WAI603-A1). Please note that you would require longer supercharger bolts and injector rail extenders or aftermarket fuel rails.