There are BMX adapter plates, for replacing a brake with a center bolt, with V brakes ..
But. given the direction the forces are applied , it would have to be mounted on the back side of the fork..

they are used on the back of BMX bikes , so forces push the adapter into the seat stays for back up..
when it flexes.

it is a possibility .. (NB still a rim brake )


Disc brakes buy a new fork .. add up 2 wheels a fork the discs and levers ..

then compare the sum of those parts buys, [& Labor to have it done right].
with just buying a disc equipped bike already set up and ready to ride..