Jojoba is a really good choice because of it's anti-fungal properties and it's ability to dissolve sebum.
I'm assuming that your client knows it's dandruff for sure which is a kind of fungal infection.....as opposed to calling it dandruff just because there are flakes present?
Going by that, your original idea of coconut oil would also be a very good idea because that too has anti-fungal properties, as does Neem oil, but that really stinks.
Bhrami is excellent, but bear in mind it's a herb extracted into an oil.....another name for it is Gotu Kola. If you buy one of the Bhrami hair oils it could very likely contain mineral oil so be sure to check the ingredients. A better idea might be to get Shikakai oil, again check the base oil as many contain mineral oil....but there are sites that sell it extracted into coconut or sesame oil. It's mainly used in it's dried herb form as a hairwash but people do find the oil extraction good too.
One thing to consider, whatever oil you use, by the description you gave it sounds like he really needs to address the cause of the scalp problem and may need a more frequent scalp maintenance plan than you can really give him as an indian head massage therapist/