I am seeking for a digital clock typeface in which the characters (I just need the digits) have the same width. I'll be using it for a countdown so if the digits don't have the same width the countdown I am building will be changing its width every 1000/60 milliseconds (NOT A GOOD USER EXPERIENCE) and that's exactly what I am willing to avoid. Thanx in advance.
You need what's called a monospaced font, or a fixed-width, font.
Wikipedia has a sample page of monospaced fonts, to get you started. On this page, you'll see a wide range of aesthetic choices. You can choose something that conveys the feeling you want, for your clock and your context.