Flexible drive plates should have a part number stamped into the outer edge of the main backplate. Given this part number, we can usually identify the specification and quote price and availability.
If you are replacing a ‘spring’ type drive plate, exact replacements are sometimes available. If not, a flexible drive plate is usually an option. Either way we would require the outside diameter of the plate, number of fixing holes and their diameter and P.C.D. Also the gearbox type and maximum horsepower and maximum R.P.M. of the engine.