For the kids to use, I make up sets of glow clip, wire, switch, and two D cells in parallel.
But I often have to make 50 or more starts in one day, and want to know the status of the battery. So I made a LiPo version as shown in the photo.
I bought a DC/DC power supply on Amazon (made by Drok) that has a capability of 4.5A. It has adjustable output current limit and adjustable output voltage.
https://www.amazon.com/dp/B07FL6PBZF?ref=ppx_yo2ov_dt_b_product_details&th=1With the display, I can always know the voltage of the LiPo, as well as if the glow head clip is making good contact.
I set the output voltage to 1.4V and the current to 2.4A. This covers all of the Cox glow heads. (One of the high performance glow heads is only at 1.2V when it is at 2.4A. If it went up to 1.4V, the glow wire would get too hot, so it will not start because it only oscillates back and forth. So having both current limit and voltage setting makes sure all the glow plugs operate well.)
I use a 1500maH 3S battery that easily lasts all day. The battery is on Velcro, for easy swapping.
The power supply includes its own power switch, but still has some idle current when off, so I added an external SPST switch.