Examine the end of the rubber wiper: this is what you'll have to match. Unfortunately no guide will help you directly, but many beam wipers seem to use a completely standard rubber pattern. In the example pictured a refill from PIAA worked just fine.

Cut the new refill to length, if needed.

Use the topmost set of slots in the refill (farthest from the wiping edge). Slide this into the two rails.

Clip the end cap back on to finish the job. Congratulate yourself on a cost efficient and environmentally correct replacement job.