You should take a look at T1-3/4 style instrumentation lampholders from the electronics industry that take #327 lamps. These lamps are rated at 28 volts and are cheap and tough. billions of them were used by the military and electronics industries until LED's were invented. There's even a box of 327's on ebay for another 10 hours for a buck
Item number: 4640482195
Mouser has T1-3/4 lampholders, part number 606-5131-038 fpr about $5 each. Then lenses are available in any color, 606-131A-303 (a,r,g,y) for clear lenses and
606-131a-304 and 404 for other variations on the lenses. these holders have pins that will require soldering.
For non-relampable plastic lamps that have wires and just push into a hole, Mouser has indicator lamps made by CHicago Miniature for about $3 each. the part number for 24 volt ones is 607-1090A(1)-28V for red, change the (1) to 3 or amber and 5 for green. These are domed lenses; for flat lenses change the A to a C. These all sitck in a 1/2" holewww.mouser.com