If you google "buy facebook ad accounts" you will see a few marketplaces. Since what you need is an account to set up a Facebook Business Manager account, you could use family and friends that aren't planning to ever use their accounts for business. Once you have a Facebook Business Manager account created from someones account, you can build up to five add accounts.
The key is that you want to use a good cloaker. This hides your real ad from Facebook and takes them to what is called a safe page, Everyone else clicking on your ad will be taken to your landing page. Some cloud based trackers now also include cloaking functions for no extra money. Chok Dee Kup