Hi, without spending out on a soundbar with a headphone output (of which there are a few, but maybe not what you want, or can budget for) You can simply purchase a digital to analogue switcher. This box simply goes between the optical digital output of the TV and the soundbar but affords you an option of plugging in a set of headphones! See this link to get a good idea of what i mean:
https/www.amazon.com/Tendak-Digital-Converter-Adapter-Switcher/dp/B0119OKOJC
Have a good look at the pictures, and hopefully you can see what i am describing.
This means that you are free to purchase ANY soundbar you wish (that has an optical input) knowing that you can have the luxury of plugging in headphones!
Hope this helps, and if you wish, i can post up a couple of soundbars that have the illusive headphone output!
Regards,
K.