B+W and Heliopan still list common push-on filter sizes as being made (at least on order), and the A32 or A37 push-on filter sizes of the different 532 lenses both are as common as can be. But you may have to order directly from the factory, the nearest distributor or through some expert mail order shop, as the common kind of digital-heavy photo store won't handle obscurities they cannot order through a point and click interface.
Coated Zeiss Ikon filters are still good by modern standards and are far from rare, these sizes having been common to many of their cameras, so ebay is another option.