12V Low battery indicator that has minimal power draw
That is exactly the wrong approach. What you want is an LED which is on when the battery is good. Even better, you want an LED which is not powered by the battery.

Using your approach, if for some reason the indicator is ignored then the LED will eventually completely discharge the battery, and with SLAs that is A Bad Thing. Granted, this can take a while. If the LED is the primary current drain, then a 5 mA LED current will waste .12 Ah per day, or about an Ah per week.

If you must do it with an LED which is on to indicate low charge, at least make the LED blink rather than be on steady. A flash rate of .2 seconds on every 2 seconds will draw 1/10 the average current as a steady LED, and will arguably be more noticeable.