Where can I find BTC sellers?

I’m looking for a seller or institution that can provide BTC. Specifically, I’m aiming to buy between 20,000 and 50,000 BTC in a single transaction and am open to discounts based on volume. I’ve already checked OTC trading desks and P2P marketplaces, but I’m looking for sellers who are legitimate and verified, with experience in handling large orders.

The transaction will be fully legal, with the necessary verification and a physical meeting, if needed. If you know any sellers or platforms that can facilitate this, please let me know. Any recommendations would be greatly appreciated!