There's sort-of and not so sort-of searches you can do on the site.
At the top of the site there's the "Members" button and you can scroll through or use the search within it to find members. These will only be the members that registered for this site since it started I think back in the summer of 2019. So if they haven't come on the site since then you won't find them there.
(The "Search" button at the top will give similar results, but I think also includes the general call sign directory.)
Otherwise at the top left of the site there is the "Navigation" box and you can click on the "CT Directory" and see lists of members by call sign number. Some of the 'older' numbers will be a link to the old tap-a-talk site and appropriate directories by call sign number too.
Not vastly helpful I know, but it's as they say, "the best we got".
(Our voluntary admin did a grand job to collate what they did do!
If you're really desperate you could put up a posting in the general chat section and maybe someone would know who you're looking for.
All the best,