Stickers advertising your services. You only need to find 3-5 regular customers and they will make you within 1-2 months the best advertising, just do not let them down in the quality of goods.
Obviously, the situation needs to be addressed. But I know that you are a responsible buyer and always take a lot and often. I just have one question, why didn't you use escrow?
Proton cooperates with law enforcement agencies and makes no secret of the fact that it passes user data to them if they receive such a request. Who decided that this is a safe way to exchange messages?
There are no absolutely secure systems. Any tool that calls itself secure is still a compromise between security and convenience. However, you need to be reasonable and not invent something that LE will never do, since the solution you described is ineffective.
If you are so afraid of Google...
Then what is the point of encryption if the server owner owns all the private and public keys? Who is the data encrypted from?
The question is rhetorical. It is unequivocal that in any implementation of text encryption "on the fly" using PGP is not safe for anyone.