I'm still a little old fashioned when it comes to thermometers, I still add the traditional analogue ones to all my tanks. That being said, I don't use them so much.
I managed to get a box full of digital ones when my friend shut his shop some years ago and I've still got a dozen or so. I'm not sure of the brand name but I'll put a picture of them for you, they are easily found on eBay and Amazon I believe.
I also have a calibrated IR temp gun which I use more often than not. I'll add a picture of that too, but it is not really needed. I mostly have it for checking basking spot temps for my reptiles, and it's mostly habit and convenience that keeps me using it for the fish tanks.