That being said, I am not familiar with the other vessels in that frigate class. Armed with the names of the other frigates, another search may well turn a KNOX class model in paper. This will only help, I suppose, if you'd be alright with building a kit that isn't specifically the KNOX: same ship possibly with just a different hull number on it's now and name painted on the stern.... Hope this helps...
Or possibly search Knox class paper or card model. HTH