Check Graupner-G-sonic and also the wooden one of Maro at:
www.lindinger.at
or
www.der-schweighofer.at

I have the following ones with thickness:
APC 14x6 has 18mm and it is a bit heavy for OS.91 anyway,
Graupner-G-Sonic 13x7 has 12.5mm
Maro 13x7 has 13.5mm.