A replacement of an older valve is always a question of several things, I presume also for Yourself and Flowserve:
1. Availabillity of suitable production equipment and material including castings, drawings and availabillity of production capacity.
2. Cost of production and and obtainable salesprice.
Flowserve is a world-wide company, and if you do not get an answer from your local representative under threat of complaining centrally (remember that a correct answer could take some time, so ask for when you can expect an answer or require an answer within reasonable time), you could do following:
Ask (through main office of Flowserve?)for minimum quantity for accepted order: (five? ten?) and compare the price with the cost of other replacements or specially machined alternatives. (Some companies specialise in making 'tailor made' products, but it will cost), last alternative is of course to alter your construction to include valves of newer type and other brands.