A "D" cell to add a power supply to those devices that run on them but have no external power connections. This has an Ebay LM2596 adjustable regulator that is set to the required voltage. Print other cells as needed to fill the battery compartment, and just have a connection from one end to the other.

I printed the first one and found it was the wrong way around so it has been mirrored to fix it. You can see this in the "straight through" cell pictured.
It could be the cells are a little long as they are fairly firm in the holder of the toy sewing machine I've tested it in but it is working ok.

Later, I may shorten it by a mm or so.

This thing was made with Tinkercad. Edit it online https://www.tinkercad.com/things/dwT8uG6CFeq

Deltaprintr

Deltaprintr Kit

Yes

No

.2

100%

This was printed with "Aldi" PLA and at 60mm/sec so is a bit rough, but good enough.