You'll find a lot of rhythmic notation here:
www.paulnas.eu/wap/

It's not specifically for ballet style (by which I assume you mean playing all 3 duns vertically with two sticks & no bells), but you can combine notes from the three dun patterns & come up with something you can play ballet style. I don't play that way much myself, as I prefer the Hamana style of 3 drummers playing one dun each, horizontally w/ bells, but sometimes when I'm on my own I'll try to figure out ways to play the interlocking dunun rhythms by myself ballet style. You can also play a sangban & bell stacked on top of a dununba (horiz.) -- you play combined sangban & dununba parts with your right hand while playing bell with your left. I always like to hear the voice of the bells in the mix.

Also the folks at African Rhythm Traders in your neck of the woods should be able to help you. Have you talked to them?

at least a few years ago when I researched this topic, there wasn't much written or transcribed specifically for a dunun set. this may have changed in recent years.

an approach is to adapt existing dunun parts to the 2 or 3 drum set. bell or no bell depends on you. generally, when you listen to a rhythm, the dunun parts form a melody. sometimes the melody is the interplay between two dunun voices, like dununba and sangba with the kenkeni playing some sort of pulse part. you could adapt this to a set by either playing the dununba and sangba with one hand and kenkeni with the other hand or drop the kenkeni part and play a bell pattern with the other hand. sometimes, the melody is between the sangba and kenkeni with the dununba playing some "walking" bass part......again, you could try and play all three parts simultaneously or in this case, you could drop the dununba part and play the sangba and kenkeni with one hand and the bell with the other.

the possibilities are endless.

many times, in modern ballet troups like "Les Percussions du Guinea" or "Wofa", there is one person playing a set of 3 dununs with no bell and a few other drummers playing sangbas and kenkenis with bells...and of course a whole "chorus line" of djembe players.....

for myself, I play with bell sometimes and without bell other times. is depends on the environment I am playing in. if I am playing at a drumcircle, the bell can be helpful to me and others as a rhythmic guide. it would also depend on whether there are other dunun players or not.

trying to cover all 3 dunun voices at once can be difficult at times (at least for me)....feel free to simplify as needed

experiment

make it fun

"when you get confused, listen to the dununs play..."

Mark