Reddit mentions of Libre Durable Glass Infuser Bottle with Mesh Strainer for Loose Leaf Tea, Matcha, Fruit, and Cold Brew Coffee, BPA-Free, 9.3 oz, Classic Silver

I CAN BE SO USEFUL TODAY!!!

The Libre Tea Mug has the exact same design as the mug you describe, but has glass on the inside, and plastic on the outside. Here's a video. There's a 10 oz version and a 14 oz version, and a 9.5 oz handled version.

However, I bought one of these and decided it's not the best thing in the universe. There were plenty of good things about it, but it had some flaws:

1. It won't keep drinks hot for very long, because plastic & glass apparently don't keep things as warm as stainless steel (not sure if this is totally accurate), but you also have to remove the lid every time you drink, and it's all the way open, as opposed to a sippy lid or other designs that have small holes or whatever, and lots of heat escapes. It also means that you get a face full of steam every time you try to drink.
   
   
2. When brewing black tea, you stick the leaves in between the two top lids (see video) and brew upside down. However, when you turn it upside down, the surface tension of the water actually retains the ENTIRE volume of water that was in the lid. Seriously. I don't know what the deal is. This happens even with zero tea leaves. This means that when you remove the two lids to drink (you need to remove both lids simultaneously if it's black tea, since the leaves are between the two lids), there's still lots of boiling hot water in the lid, and if you tap it, or bump it, or angle it, all that water falls out. You really have to tap the lid to dump this excess water before you drink; if you don't, you run the risk of spilling lots of hot water all over yourself. Someday you'll forget, and probably burn yourself.
   
   Aesthetic problems:
   
   
3. You can hear the plastic creaking against the glass, and it makes it seem cheap. Purely psychological, but it probably could be fixed.
   
   
4. The larger size and the handled mug version have the company's website printed address on the side of the lid. Pretty ugly in my opinion.
   
   
5. The lid has a picture, but it's a physical object (a tiny carving or something) and it actually moves. It's somehow not secured in place, and it moves off center and looks awkward and cheap. Plus, I can see a couple parts of it bent the wrong way.
   
   I can't really recommend it, but if you've used the Activitea and found it usable, you might be happy with the Libre. The design looks pretty much the same from the photos, as far as I can tell. But I have continued searching for the perfect tea mug.
   
   Contenders thus far:
   
   
6. JoeMoXL: Entirely stainless steel, with a removable infuser basket, a push-button seal, 360 degree drinking, sipping that doesn't require removing the entire lid and draining heat away, leak proof, etc etc. Good stuff.
   
   
7. Timolino infuser mug: Theoretically similar to the JoeMoXL, but no push-button seal, and the infuser basket has some plastic. Oh well though. Adds a hidden compartment in the very top lid where you can store sugar. Smaller than most travel mugs (12 oz instead of the usual 16), so I think it's more practical to fill up, drink, then fill again and get a 2nd steeping out of the tea, as opposed to 16 oz over the course of the day and then getting home or whatever and not making use of the leaves until the next day maybe. There's also a carabiner version. Note that Timolino makes 2 tea mugs; this one, plus another that is ONLY good for green tea, with the leaves steeping inside the main chamber, with no removable infuser basket.
   
   I've been shopping around for quite some time. These are the two winners as far as I am concerned, though they skip out on being see-through and hiding the tea in the lid, but I can't see any well-designed options out there with those traits (although this Thermos mug has the infuser in the lid, but I wasn't so excited about it), so I'm giving my seal of approval to these. There are other contenders I think, but these are equal or better compared to anything I can find. I might also just go with a Contigo and brew in a teapot and just deal with the fact that the mug has no internal tea infuser.
   
   OCD FTW!

There's a lot of them still around that have the plug-strainer insert. Some have better strainers, like the Libre tea tumbler that are part of a screw-on ring so they don't pop out while you drink. The Libre also has the advantage of having the glass-inside, plastic-outside design for durability.

I also have a collection of tumblers purchased in Beijing that have nice filters on screw-on rings, and even full-sized double-wall aluminum tea mugs with similar filters, but I haven't seen that particular design in the states yet.