s.o.s help to find a compatible cdi

[markm111273]

i`ve got a better bt125-6 and the cdi has gone.i`ve bought various replacements but none work exept a secondhand one from a breakers but this just lets the bike start and idle and as soon as i get to about 3-4000rpm i dies.i have tried the place i got it from but the one they sent me did`nt work either.they said they are all the same but i`ve been told there not.the engine number is bt156fmi.any help would be very much appreciated.atached is a picture of cdi with part number