if you are waiting for someone else to come up with something you want that isn't out there , you will die waiting, and it still won't come out.
now, you can do one of 3 things, wait for it to never come out. forget about it. or, make one for yourself.
they never made a 70 round drum for a PPs43, but I wanted one. so I took a PPSH 41 a 43 stick mag and made one for myself
they never made a 100 round drum for a 5.56 AK, but I wanted one. so I made a feed tower to go on my BETA C-MAG
I made quite a few other things that are not on the market and never will be, ie, stripper clip loaders for a PPs43, stripper clip loader for a 5.56 AK mags etc...
all it takes is for you to want one, is a desire to want one and a little ingenuity, by welding a 10 round mag and a standard mag together. there you go, your own hi-cap 9mm mag.
this isn't rocket science, 2 mags and a jig to line up everything perfectly. I used a piece of wood to line up the opening of the drum to the bottom of a cut down 43 mag.