Unfortunately, the wiring within the cable determines whether or not it's DTE/DCE. The "frame-relay intf-type dce" command you mention only affects the layer 2 behavior of the interface (tells the serial interface to act as a frame-relay dce and respond to LMI packets) and does not affect the layer 1 behavior.
A gender-changer won't help you here, it's the way the octal cable is built that determines whether the interface is DTE or DCE. It *may* be possible to build a custom cable to address this, but I'm quite sure it won't be worth the hassle and/or money invested.
Regards,
Clay