Buy a brand new pixel and load the new operating system yourself. I promise it’s not hard.  There are many YouTube tutorials and excellent documentation on their website. While you can buy a pixel with graphene preloaded you ultimately have to trust they aren’t trying to rug or spy on you and didn’t do it maliciously. Which they probably did tbh. 
Personally I would run an iPhone in lockdown mode with a VPN before I bought a preloaded graphene phone. A preloaded phone is just highly suspect.