Here is a list of left handers currently in the 2020 Mets’ bullpen: Justin Wilson. That’s it.
The Mets didn’t have any kind of luck with bullpen lefties last year. The only non-Wilson left-hander still with the team is Daniel Zamora, who is most notable for, in order (as I wrote in my 2019 recap): “That’s Amore” jokes, inexplicably being brought in to face Bryce Harper and eventually taking the loss in the the September 1 game against the Phillies that effectively ended the 2019 season, and being a lefty without notable splits against left-handed batters.