They appear to be the same diameter as the rOtring Rapid erasers. If so you can buy these General Pencil Company BM-2 eraser refills and cut them to length. (Each package of three should make 24-27 erasers for the 925.)

Erasers for Staedtler pencils (General Pencil BM-2 refills)

I bought these and can confirm they fit the Rapid Pro, Sanford Technician II and PaperMate Apex, Staedtler 925 (75 and 35, the latter when using its metal "clamp" or whatever it's called).