Good luck on finding one that is in the Glok $10-$15 range. A simple OWB Belt Slide Kydex holster would be just as good, if not better than the Glok holster, but it would most likely cost more than the Glok.
S&W includes a Blade Tech holster in their M&P Carry & Range Kit, I think it's called the
Revolution, but it's around $30.