Sep 25, 2018
I've received the correct knobs now and they do fit but are too loose on the spindle to stay put so I've had to DIY it a bit with a tiny bit of Blutack in each one so they stay on! The knobs are for the TS4/8 and I've got the T1 (the model that those models have superseded; I was told that the knobs for the T1 are no longer available) so I was fully aware that they may not be a perfect fit. Works fine though.
Just thought I'd give you all this info so any other T1 users are aware.
Jul 21, 2021
Hi Berto162 and welcome to the Pro-Portable Community!
For replacement parts like the volume control knob you mentioned, you can contact Bose Support and place an order. To find the right support contact for your region see this link - https://global.bose.com/en_us/support_sites.html
Hope this helps!