I would suggest seeking intros from attorneys/CPAs in your network, checking out your local SBDC, SCORE office/site - or (shudder) check with the SBA. Like patent attorneys, grant writers would probably be categorized under small biz service providers (which are often single entrepreneurs).
Your mileage will vary as far as what incentives they'd offer to win your business, but there's no guarantee of award. Therefore, I think it's highly unlikely that someone you're meeting for the first time will offer special/deep discounts. You'll have to review their prices and maybe get multiple quotes...
Take heed - this form of "free money" can be very expensive (even if you happen to win).