There is an undocumented endpoint you could use https://tmi.twitch.tv/group/user/{channelName}/chatters which will show you the mods that are currently in chat. I don’t know if there is a way to see a list of mods that includes those not in chat at the time though.
Keep in mind though that because this is an undocumented endpoint it’s not officially support and might break/change at any time (and in recent days has had some issues).