Lol I love those trans backpacks.
I've tried various containers and lockboxes, especially because people have expressed horror that I would keep needles unsecured in a home with a teenager, but I finally settled on just keeping my supplies in a drawer near my computer. Nobody in my life likes shots or enjoys hormone swings, so I think the desk is secure enough. When I had to open a locked or hidden container to get my T and supplies, it felt too serious and it made me more prone to delay taking my shot on time. It also felt kind of shady and covert.
Because even sharps bins designed for insulin needles tend not to fit in drawers, I've had trouble with forgetting to hide them. I once had a visitor notice and she was alarmed enough to "put the lid back on" as a favor to me, but it was the permanent seal that shouldn't have been closed until it was full. Now I have a shoebox-sized one and it's actually easier to deal with. I stick it under the desk or under the bed when I'm not using it.
I keep cat meds in the fridge but never thought about doing that with testosterone. Now I'm wondering if I screwed myself over at all by forgetting about temperatures.