No it's a totally different size, 550 vs 650. I've had both at one time long ago.
I think the magnet-rotor aka flywheel from a 750-four, which still comes in 4 sections like the 650, may be more powerful and will fit the 650 crank, but you will want confirmation of that before trying it. I don't want to send you down a rabbit hole of experiments and spending money when all you want is for the bike to charge. Maybe someone who has swapped a full 750 charging system into a 650 can chime in.
Or if someone with a spare 650 rotor could loan you one to try, that would be nice. If there is a cheap one, 750 or 650, it might be worth a try.
Or does ricks or electrosport offer a heavy duty 1-phase stator for the 650? That's probably not going to be cheap for sure.