Lee, 31, who retired from international duty last year, will replace South Africa allrounder Nadine de Klerk after she was called up for the tour of Pakistan.
An experienced opener across formats, Lee featured for Trent Rockets in the most-recent edition of the Hundred, scoring 165 runs from seven innings.
The Blaze, who also play at Trent Bridge, currently sit top of the RHF Trophy standings, with six wins from 10 games.
“I am very excited to join up with the Blaze, particularly having played with some of my soon-to-be team-mates during The Hundred,” she said.
“They have been playing really well across all competitions so far, and I hope that I can contribute and help push for qualification in the Rachael Heyhoe Flint Trophy.”
Chris Guest, the Blaze head coach, said: “Lizelle is a great addition for us as we get to the business end of the competition. We’ll benefit not only from her skills, but her knowhow in big games too. We’ve seen plenty of times how destructive she can be on her day.
“We are in a good position with our focus solely on 50-over cricket now, which gives the team a real energy and drive to finish the season well, and Lizelle will add impetus to the group.”