Rubber eye cap for view finder.

Forgive me if I don't know the correct name for the accessory I'm after but I'm hoping someone will understand my description and advise where I can buy one from...I have seen on many Canon camera users a rubber eye piece/cup they fit to their viewfinder...helpful for wearers of glasses...would like to get one for my Penatx K20d but not sure of their name and who would sell one. Thankyou in advance.

I brought one of these for macro use, although I do not wear glasses I find it more comfortable as it creates more space between the camera body and your cheek, magnifies the image and provides a soft eye piece.
click here

Ebay is the way dude

Avoid the one discussed in this thread:

https://www.pentaxuser.com/forum/topic/Eyecup-for-K10-12537/p-0#comm_122210