I use Brotect Airglass from protectionfilms24.com and I can highly recommend it. It’s a flexible glass screen protector. 5,79 € for 1x, 7,99 € for 2x and 10,99 € for 3x.
When I first ordered it, I realised during the application process that the screen protector was slightly too big, which cased it to not sit flush to the screen (since there is a small ridge around the FP4 screen). I contacted customer service and forwarded my complaint, which resulted in them altering the product and sending me an improved version for free. With these alterations, the screen protector is the perfect size. Thumbs up for a good product, two thumbs up for stellar customer service.