Hi Tom,
The two best generic sources online [for me] for searching convoys are definitely the Convoyweb site and the Warsailors site:
http://www.convoyweb.org.uk/ [they also have a tab for 'convoy finder' which lists the ships in the convoy] Siri's site:
https://www.warsailors.com/convoys/index.html
None of which are complete but they are very good. You can also use movement cards to cross refer individual ships.
As far as TNA is concerned there are official document in the ADM series which is not available online.
There are of course written works such as The Winston Specials: Troopships Via the Cape 1940-1943 which has favourable feedback.
Regards
Hugh