Ok unless you want 12 volts i would go with the one of the 81 TS125 ER type stators. which will give you you about 25 to 30 watts @6 volts AC for head and tail light. Then there is a trickle charging circuit for small 6 volt battery. Because of the trickle output no regualtor is used, but i believe that the headlight on off switch is posibly configured so that when the headlight off in day time the battery isnt over charged or that may have only been on the 70's models. Its complicatrd so i wont go into it here.
Its is possible to to convert the lighting circuit 12 volts but because of the type os system it is its not quite as straight forward as it sounds especially if you want to keep a battery circuit. I have modifyed my TS185 ER stator by getting rid of the battery coil and fitting another light coil off a 12 volt TS185 ER but a early 6 volt coil could still be used. I linked both in parrallel and it gives a decent amount of power for lights now. The catch is i no longer have a battery or blinkers. if i really wanted to i could have blinkers without a separate battery circuit, by either using filtered AC using a bridge rectifer or AC flasher unit, but this type of set up will only work well with LED globes in the blinkers. any way im probably going to be confusing you soon?.
other possible option is to see if a TS125 ERZ (1982 air cooled motor, full floater suspension) stator will fit. They are a 12 volt system straight up and use a modern type regulator rectifier. Unfornately i havent got a decent clear digrame of that stator but it cas the coils arranged in a cross type pattern and there is either 3 or 4 coils im not sure yet. UK had these models and i thin australia did. NZ did. USA didnt have any TS's after 1981. These 12 volt air cooled motor TS 125ER's contined into the 90's in some countries. i saw on on NZ trade me a while back. but dont get them confused with the water cooled TS125 X which came out in 1984 or the water cooled TS125R which came out in the late 80's
at this stage i think its gonna be a matter of go to wreckers and checking out what physically fits, or otherwise be prepared to buy a few different stators till you find out what fits, which could end up costing dollars.
the problem is with the TS125's is that thers that many different models and different countries had different version and ran different magnetos and some countries continued running the older model bikes longer than other countries while they instead had the newer models.
