This is a hand lamp I have made. The battery I have used is from an 18v Bosch Drill I have. The original connector was for a "Power4all" battery that Bosch obviously subscribe to.

For the LED's I have used the LED replacements for car internal lights, they fit nicely in the fuse holders I had from an old PCB mounted on a piece of Veroboard (Strip board).  I don't know how long the LED's will last at 18v but there is room for a small voltage converter board in the handle if I find they don't last long. The LED's draw about 0.13 Amps, with the battery I have fitted they should last about 10 hours.

All printed in PLA, supports needed on the body and battery connector. I put support blockers on most of the body except for the 4 ventilation slots, the other places support was automatically added was handled by the overhang settings. 

The Battery connection was from a project on thingiverse: https://www.thingiverse.com/thing:4719450/files. 

Please also read the battery warnings at https://github.com/usedbytes/power4all

The most difficult part was pushing the spade connectors in place, I used a soldering iron to melt them in and hold them in place.

There is no mounting holes for LED's as it will depend on the LED's you choose to use. I drilled a 4mm hole to take a brass insert to mount the Veroboard I used.

The wiring is simple, both switches are in parallel and only the positive side is switched.

The parts I used were 

Momentary push switch:https://www.aliexpress.com/item/32965803216.html?spm=a2g0o.order_list.0.0.3c081802Tm6YC3

Rocker switch: https://www.amazon.co.uk/gp/product/B07YD8BM28/ref=ppx_yo_dt_b_search_asin_image?ie=UTF8&psc=1

Fuse Holder(similar to): https://www.aliexpress.com/item/1005001604320468.html

LEDs (Left over from kit): https://www.amazon.co.uk/Kinstecks-Can-Bus-Interior-Courtesy-Instrument/dp/B08DHF9FYS

All the parts fit together using Brass inserts, there are 4 in total not including what you decide to use to mount the LED's.

The lens should be a push fit depending on the tolerance of your printer. I used this hint to try to print the lens as clear as I could but it still came out more as a diffuser than a clear lens. https://www.printables.com/model/15310-how-to-print-glass

When fitting the terminal cover on to the battery connector make sure the countersunk  screw you use fits flush or you might have trouble getting the battery off!

Please heed the warnings about the battery usage as there is no protection for over discharging the battery. Also there can be a fire risk if you short the battery connectors! 

I would also not recommend using filament bulbs as they can get very hot and will melt the body of the lamp