I think what you're looking for is something like a preliminary interview round that is cheap for you to administer, combined with a financial reward for those

I think what you're looking for is something like a preliminary interview round that is cheap for you to administer, combined with a financial reward for those you select to go to the next level of the process. For incentive reasons, the budget for this must come out of the hiring company's recruiting budget. Otherwise, it's a great way for unethical folks to extract money out of the applicant pool. An alternative way is to set up some sort of competition with prizes, and then recruit from those who do well at it.