I usually go to the online store like amanzon, DX and Tmart. Their products are cheap and nice. BTW, Tru seems to be an interesting site. However, I would not like to pay $10 to buy a screen protector film. I bought 3Pcs Screen Protector for BlackBerry 9930
(which is the same size with 9900) with $1.96 FS at tmart.
It was not so hard as I imagined to stick a protector by myself.