Sept. 2-13 is waitlisted 
Sept. 14-25 has 1 seat open.
You might call the RS office and ask them when the season ends for the gondola to Italy.  My tour missed it by 3 or 4 days.  9/18-9/29/2023.
There is a website which I just typed in:  Aguille du midi gondola to Italy.  It might give the last day the lift operates in 2026 or it might be too early.  I think you would be safe with the Sept. 14-25 tour but I would confirm that.  If you don’t get to do this, you will still experience the thrills of what is open.  Gorgeous scenery!
Another thought - sign up for the Sept.14-25 tour to get the $100 early signing discount and put yourself on the waitlist for the Sept.2-13 tour.  Then you can switch if you want to.  RS makes it an easy process.