I am looking into this myself, but i think not in the same way you (Lasagafield) want to. Here are your options :
1
Make them using parts for DIY transformer construction - E/I plates and bobbin
Advantage : The best quality ballast you can make (without special equipment)
Problem : Ballasts need an air gap of a determined size in the core. In transformers the design goal is opposite, to eliminate the gaps as much as possible. The laminations (steel plates for the core) made for transformers are specifically designed for the latter. There are ones designed for devices with a gap, but are not as widely available
2
Make them in the "big gap open core" design (cheap crude FL chokes from the 60s/70s)
Advantage : Very basic design, simple, forgiving to bad precision, probably forgiving to bad quality steel
Disadvantages : Not precise (lamp current may be off the mark), very leaky magnetically (so tend to be buzzy)
The design/calculation theory is straightforward, but still, i guess we gotta be prepared to waste some copper wire and possibly blow a tube or two in the first attempts
There indeed is no material about ballasts, but there is about transformers, so that should give you a start
Here is one :
https://ludens.cl/Electron/trafos/trafos.html
Check out the stuff and think what you actually want