hmm, after you added the usb controller you should be able to add an usb device. Same way as adding the usb controller.
Maybe one of the prerequisites is missing like vmHarware Version minimum 7 or USB2 (not USB3) port/device (http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1022290)?