My Reduce Wedge thermos keeps hot tea steaming hot for over four hours.

It does a better job than any thermo my hiking partners have tried over the years.

Here's one on E-Bay for $10:

[ebay.com]

I have a large thermoscafe by Thermos I’ve had for over a decade. Works great for night shifts for keeping my tea hot.
If I’m just going to a sports event or something where I can have an open drink, I have Yetis for that. They’re good too.

Word of mouth says Yeti.

I also had good luck with a Stainless Steel Thermos. Made by "Thermos". But that was decades ago. (It still works though). Nothing to break either.

[ebay.com]

...of course, all stanley thermoses are good.

If your budget is large enough ($80 on Amazon), the Ember Temperature Controlled Ceramic Mug looks interesting. But, it isn't a thermos. It's just a mug.

My nephew and his wife both use Yetis for their coffee. They swear by them.
I've heard they're expensive, but last a long time, and keep hot liquids hot, and
cold liquids cold.
So, I think this is just another instance of "you get what you pay for".

The ones made by Yeti are very good but pretty expensive.

[littlecoffeeplace.com]