You can get a decent little drawing tablet for $30 these days. You'd probably spend half of that in the cost of pens over the device's lifetime. They're no longer ultra-expensive specialized equipment.
Can you suggest a model?
Osu! Style drawing tablets are also a thing but they are small, maybe you want to spring for a slightly bigger tablet.
I don’t get why anyone would subject themselves to the pain of drawing with a mouse.
Plenty of cheap ones out there that work with most touch sensors