Are you looking for where he was buried, or when he died and where he was buried?
If you have not found his death, how do you definitely know that it was in Sunderland?
Have you got the death certificate for his wife, and was he alive then? (As she was a lot younger than him, probably not) Have you found the wife's burial place?
Had a quick look for her:
Possible death for wife
Elizabeth A Mawson, age 67 died September quarter 1923 Rotherham
which then fits for a possible death for him
John Mawson age 84 died March quarter 1927 Rotherham
In which case he did outlive her.
Or have I tracked wrong family - sorry got to go now so cannot recheck for a bit.