On your Delta DPS60M power supply, why not open the case and look? If it is in-fact a glass bulb in a socket, the part number may be on the bulb. If not, measure the voltage on the socket to select the appropriate replacement bulb. You may have to start with a low wattage bulb to keep from drawing too much current and see how well the meter is illuminated. If the illumination is by a LED, you may have to trace the lighting circuitry to get voltages and components and do some calculations to see which LED would be a replacement candidate. Also check the LED to see if it has any markings. Since your meter is apparently not illuminated now but used to be, the problem is probably from a burned-out bulb. LEDs have long MTBF values. Finally, you could also consider changing the bulb to an LED arrangement. That task would not be hard at all.
<edit> The schematic for that power supply can be quickly found by a Google search. Note that the image may be copyrighted so I cannot post it here. Google “Delta DPS60M Schematic” to find it.