IIRC they can name a new candidate. Though it’s likely too late to get that candidate on the ballot everywhere, and votes for Trump can not just be counted as votes for the new candidate. If Pence is the candidate, then votes for Pence as VP can not be counted as votes for Pence as president.
So it’s basically a last minute write in campaign.
However if Trump kicks it post election, and he’s won. Then Pence as the winning VP would become president and the new Congress would select a new VP.