Just installed (well 50% of the way there) a newer Truvativ GXP Elita crank with a "gigapipe" bb - which I think is the same a Hollowtech II?

I'm missing the non-drive side crank arm bolt(s) - there isn't one on the drive side as the spindle is mated with the crank arm...

Anyway, I'm a little confused about exactly what I need.

I've found this thing (pic attached):
http://www.ebikestop.com/truvativ_gx...cap-CR2193.php

The crankset is the same as found here:
http://cgi.ebay.com/NEW-TRUVATIV-ELI...QQcmdZViewItem

Does anyone know where I can I order one cheap?

Thanks for any advice.