I have searched every variation I know within the surrounding areas, and cannot find them together in 1841

Perhaps others will have more luck, but it is doubtful.
The BMD site gives the GRO ref numbers, you have to purchase the certs for additional info and hope it is correct.
Sorry but there is no other way I know

I only wish....this can be a very expensive hobby.
Info can be found on the IGI/familysearch.org site but unless it is extracted from records, not submitted, the info cannot be trusted.
I have also included a link above for the area David was born.
The only other is Glamorgan Records Office which may charge for look ups if you cannot get there in person, you can google for email address.
Regards
Cas