Here in England, I just got one from Evans. Seems to work okay, not too wide nearer the saddle so my legs don’t rub against it.
I still put a towel of the top of my bars as added protection. I wouldn’t use it on it’s own.
They are also called Bike Guard Sweat Protectors. I have the Saris / CycleOps “original” version. It has two pockets that are great for holding a remote and fan control. The guard seems to be effective. Even when there is “holy water” all over the floor during my rides the bike top tube is never damp.
Here in the states I use one from Blackburn. It’s called a bike thong. I also keep a sweat towel over the bars that I use and replace every ride. Taking apart the bike for a clean last month, I realized I needed another draped over the front tire, brake, and wrapped around the cable inlets to the frame. Yeah, I sweat a lot. Holy waterworks!
I’ve had two. The current one (Tacx) has a pouch to store my phone. I’d recommend the variety with a pouch. It can be really useful for long relaxed rides & races.
I’ve actually removed the front brake. Check the quick release skewer opens and shuts fine. I religiously cleaned my bike and forgot the skewer joint, which seized. Had to cut it off.