How about KEH.COM as a place to look: http://www.keh.com/camera/Large-Form...990008120?r=FE

380 F5.6 WOLLENSAK RAPTAR ALPHAX SYN BT BIPOST (15') (8X10) LARGE FORMAT - 380 F5.6 WOLLENSAK RAPTAR ALPHAX SYNCHRONIZED FOR FLASH BULB, TIME BIPOST (15') (8X10)