You could always ring the vicars of Broadclist and Bradninch to see if they still hold burial registers for the dates you know, (small parishes so book takes longer to fill up!!), If they do and are willing to check for you, would suggest you ask them for bank details so you can make a small donation.
If not ring Devon Heritage centre, and they can search for you if the burials are not on line. There will probably be a fee for that. Failing that, if you can get to the churchyards and tramp! does not guarantee there is a stone.