Here goes something. If I were you I´d go for the swtching step up regulator, for a more professional solution. Any way, if you are itented to make a cheap, home made solution this could be good for you. It´s a 555 used in astable oeration followed by a rectifier that will produce -Vp. That´s very usefull in most situation but if you need 15V you could just take -V as you groun refecence and than you´d have 16V between +V and -V.
As I said, it´s not a solution that I´d take in a professional design it´s just a hint for a cheap, home made project.