Like Ted said, you can get in touch with the schools and they will send them to you.
The game tape is better over all,But most of college teams play only two kinds of defense in the back end and most teams keep the SS and FS way off the ball even when you watch the games on Tv you can tell if they are about to go into a cover 3 or not, and with that you know where people should be........so you'll know if the DB's are where they should be.
I use to get the schools to send me tapes a long time ago but nowadays you can always find the broadcasts here or there and if you watch a DB play 10, 20 or over 30 games you'll know if he's good or not..................but then again you really don't need to see very much of a good player to know he's good on game tape or on TV.