How about feeding a PWM signal into the transmitter, and pause it when you want a trigger.
RX side can output a 1 all the time, and when signal goes away for 1 or 2 cycles output a 0.
Speed up the PWM from analogWrite()s 490 Hz frequency to 2K, 5K, something in that range, so each incoming pulse is occurring every 0.5mS or faster. Have something like a watchdog timer going on the Rx side.