Hi David,
If the records are not with the NAS then it's very doubtful that they have survived.
I don't think the UP church at Bonkle ever had a burial ground, the parochial burial ground at Cambusnethan would have been used. I have some records for that ground, so if you post the names you are interested in, I will have a look for you. Full names and maiden surnames please.
Lodger.