Typing an arrow (→) the way I always do: ctrl-space into Japanese IME, type "yajirusi" (= arrow), select the direction I want.
I wish we had input methods for alphabetical languages that filled this gap between glyphs common enough to warrant their own key or Vulcan nerve pinch, and those that are used so seldom it's not onerous to look them up in a table. It would be handy for things like currency symbols and mathematical operators.