Surprised this doesn't exist somewhere. A few:
'51 WC: Ragozin and Flohr for Botvinnik, and Alexander Konstantinopolsky for Bronstein.
'72 WC: Lombardy for Fischer, Geller, Krogius and Nei for Spassky
'13/'14 WC's: Carlsen has rotated many people through the position, Hammer seems to be a constant, also had Fressinet and Adams in the '14 match. Anand used Sasikiran, Wojtaszek and Gajewski in '14 match, Leko and Chandra '13.
WC match narratives often seem to mention seconds, but no time to dive them all.
Also surprised how often they were unknowns--GMs, but not top-50 types. I guess you don't want to give away your prep to someone you're genuinely worried about facing in the future.