I used to have some older rack and tray combinations, but they were from before SATA, and had these cheap locks with keys that were so shallow the keys fell out all the time. Are yours like that?
I'm mostly using Western Digital RE SATA drives, but I have some IDE drives also, WD and Maxtor.
I looked at Computergate.com and they seem to have two price levels, $30+ and around $15. Which ones are you using? Computergate.com doesn't have many photos so I can't tell if the racks have key locks or some other kind.