What about a water bottle holder with a belt loop then? Something like this. It has a clip as well as an adjustable belt loop. Or you could just get any inexpensive water bottle holder/sleeve, add a belt loop to it and then feed it through the waist straps of your bag.

I have tons of DVDs too but I took them all out of their cases and put them in plastic sleeves so as to save space. I put all the sleeves in DVD boxes I get from Ikea that way they stay sort of dust free and hidden from view