Another option is to check the type of plastic your fairing is made from - you may be able to chemically weld it. On my 500 and 900 the fairings are ABS - I dissolved some lego blocks in acetone, used a dremel to clean the areas to be mated and applied the sludge carefully.
Because it melts the existing fairing and fills any gap with the abs (lego) it effectively becomes one piece

Allow it to set, sand back, fill (if necessary) and prep for paint.
Q-Bond has also been recommended to me but I'm yet to try it - have it sitting here ready to go tho.
plasti weld is another option....I just wasn't very good at it lol