C Zeiss Jena Jenoptem  10x50 £9 each. PPI £3.95 for one or two.They also fit the Dekarem but see photo.
The original eyecups have not been available since 1990.

C Zeiss Jena Jenoptem / Deltrintem 8x30 22mm thread. 

Careful as other sizes exist especially 29mm on Japanese models.  £9 each. Plus PPI £3.95 for one or two.