I think any card for boss's day will do...maybe a nice thank you card or just a an all occassion card with a computer generated sentiment "Happy Boss's Day". I guess I better go and make one for my hubby's boss!
Here a gallery link for some ideas:
Gallery at Splitcoaststampers
I guess you can use a coffee stamp set if you have one since most people drink coffee and it could be used for both a man or woman boss. Good luck!
Boss's Day is on October 16...