Dallas Joseph posted:Stan , is there any specific type of LED BULB that has to be used . 🤔 ...
Not specific. There are many options as shown in above photo from the linked thread. I'd say mainly depends on mounting hole size you have or have drilled out. In any case, costs are modest...pennies or maybe a nickel or dime for a suitable Red LED, a penny or two for a resistor.
Additional comment. You may run across so-called "clear lens" Red LEDs. That is, when unpowered the lens is see-through or clear. To each his own, but for marker lights I prefer the "diffused red" lens style as is the case with all those in the above photo. That is, when unpowered the lens is red.