yes they exist, just google for casing, or external enclosure.
for dvd you will normally need the 5,25 inch version, might be it fits a 3,5 but the information with the casing tells you that.
beware that casing prices vary. I have seen exactly the same item from the same manuf, under different names, for 10 bucks, and over 40. this example was for a laptop hdd casing.
what you also have to think about is if your dvd player needs ac power or not. I will buy one in the usa that gets the power from one or 2 usb ports and thus draws its power from the tablet battery.