Mirrors are (relatively) cheap. Buy a helmet one, and if you don't like it, replace it with a handlebar one. Forget about whether it's weird or not, anyone who cares about what you have on your bike is going to find something to complain about and should be ignored anyway. Personally I prefer the helmet mirror as the vibrations on the handlebar one I tried made it difficult to see very much, YMMV. Be aware that it takes some practice to make any good use of the helmet mirror, but once you adjust to it you'll find it comes naturally.