I bought mine from edited out because I realize this wasn’t a pm lol, they test every batch they sell through janoshik (probably the most respected peptide tester) and include the results. They also reimburse members of the community who send their own vials for testing as a way to show that they don’t bullshit the results. You can take a look at their telegram channel. In terms of US vendors this is who I would suggest, you just have to wait for them to do presales for the GLPs for the good prices.

Otherwise there’s stairwaytogrey which is where you’ll find all the Chinese vendors (join the telegram). That’s more Wild West and you have to go out of your way if you wanna get stuff tested as a group or try to find out if a batch you bought from a vendor was already tested by a group. But it’s dirt cheap.