Runewars isn't out of print, and the 2nd Edition is using the same arrows and plastic bits to fasten them on as far as I can tell (they use them in many of their games these days). The 2nd Edition mats are being printed on cardstock instead of thick chipboard, but the arrows are the same AFAIK.
That said, you should be able to carefully pry apart the plastic bits. I've done it before, on Civilization and one or two of my X-Wing dials that weren't fitting quite right. Just get something thin, hard and flat under the edge of the thing (go for the one on the back; there might be a little damage) and gently pry until it loosens a bit. Once there's enough space to get your fingernails under it, it shouldn't be too hard to pull apart.
That said, you should be able to carefully pry apart the plastic bits. I've done it before, on Civilization and one or two of my X-Wing dials that weren't fitting quite right. Just get something thin, hard and flat under the edge of the thing (go for the one on the back; there might be a little damage) and gently pry until it loosens a bit. Once there's enough space to get your fingernails under it, it shouldn't be too hard to pull apart.