Yes. On recreation.gov,
click on Inyo National Forest wilderness permits;
entry trail is Kearsarge Pass;
exit is Happy Isles/Yosemite.
You will be able to pick up your permit at any Inyo National Forest office - Lee Vining, Mammoth, Bishop, or Lone Pine. I think recreation.gov asks you which of those offices you will be picking up your permit at. Don't pick Lone Pine. If you are sure you are going to be in the town of Mammoth Lakes, maybe plan to pick it up there. Or if you want more updated conditions on the southern sections of the JMT, plan to pick it up in Bishop (although that might interrupt a good hitchhike).
From Mammoth I would just hitchhike to Independence and then to Onion Valley from there.
It'll be fantastic in September, not as crowded. A little dry this year, though.