Is yours a pan based Speedster or a tube chassis Cabriolet (i.e. roll up windows). If a Speedster (with side curtains) one by VM "may" fit. (I bought one several years ago for my CMC (step child of early IM) - sewing is okay quality and sides are a little narrower where it meats the windshield). At VM they are $493 ($380 when I bought)-
https://www.vintagemotorcarsin...e-top-stafast-cloth/
IF IM can supply one I think it would fit better. Worth email to them to check.