Any dice will work, as long as you have 27 identical ones to work with. It is best to get a few extras, since most of the time there will be a few dice with imperfections. The extras can be used for drilling practice, testing glues, etc. Translucent dice may be more expensive but provide for a more interesting cube.
For my cube I ordered 30 red 19mm translucent dice
from Uncle's Games
Inexpensive dice will not be perfect cubes, however, it is likely they will be much closer than gfixler's acrylic cubes. For the purposes of making a dice cube, its not really necessary to have anything more precise than these.
Though I don't have personal experience, I would not recommend "Casino Style" dice as they are usually made of acetate, not acrylic (the glue I used doesn't bond well to acetate), and do not have indented pips, so the ink may rub off during use or make the cube harder to turn. On the other hand, they are probably the easiest (and cheapest) way to get perfect cubes.