Contacting YT Influencers

Does anyone here have some experience in contacting popular (300k+ subscribers) YT personalities and arranging a product placement in one of their videos?

I have tried emailing 10 of them with a very attractive email (professional manner/talking about unlimited budgets, etc). But I only received an answer from 1 of them and it looks like our partnership is not going anywhere.

I have also tried looking for some companies who could help me out but I was unable to find one.

Any tips and recommendations would be highly appreciated! Thanks