Hi Michaela. I didn't find anything about William, sorry, but here is a source that you could place on the profile of his son James Douglas Campbell so as to add an exact year of death to the family knowledge already cited:
<ref>[https://www.familyhistory.bdm.qld.gov.au/ Queensland Family History]. Death registration details [https://www.familyhistory.bdm.qld.gov.au/details/dd71a6412dc54288956126ce662057b5b17dad592951a198e585b3f3deee30b7 1960/B/38690]. James Douglas Campbell. 25 June 1960. Mother: Margaret -. Father: William. © The State of Queensland 2021 [https://www.qld.gov.au/legal/copyright CC BY 4.0].</ref>
<ref>[https://www.familyhistory.bdm.qld.gov.au/ Queensland Family History]. Death registration details [https://www.familyhistory.bdm.qld.gov.au/details/dd71a6412dc54288956126ce662057b5b17dad592951a198e585b3f3deee30b7
1960/B/38690]. James Douglas Campbell. 25 June 1960. Mother: Margaret -. Father: William. © The State of Queensland 2021 [https://www.qld.gov.au/legal/copyright CC BY 4.0].</ref>
Edited to add: Because of the long URL this is hard to see on G2G. I've taken the liberty of adding it to the profile. Please feel free to remove it if it's not suitable!
Yes Michaela, Queensland BDM is free and easy to search, though images of certificates would need to be purchased. See this link:
https://www.familyhistory.bdm.qld.gov.au/