I don't believe the IR sensors are simple photodiodes, they communicate with the door opener with some proprietary protocol.
If this is the case, you might try making your own.
Modulate an IR led at 38khz, use a lens to extend range...
And receive it with either one of these demodualtors, TSOP4038 or TSOP58038.
These two specific parts are rated for continuous use, I found both at Mouser.
Regular TV remote demodulators will stop responding to a continuous signal (over 20% duty cycle) after a short while due to the gain control.