Dolpo or Mustang
I plan to do one of these treks for about 12 days from 12/13 October.
The Dolpo trek would be up to Phoksumdo Lake either via Kagmara La or Numa La. The permit is fairly easy for this area.
The Mustang trek is in a restricted area, which is more appealing. The permit is more expensive and I think you must take a guide.
I am from Sydney and traveling by myself. This is my fourth time to Nepal so I have some experience here. I have previously independently trekked Annapurna Circuit and Sanctuary and Gokyo Valley and Island Peak.
Please let me know if the dates and one of those treks interest you. I am in Katmandu at the moment.