Are you looking for more customers? The NIH grant database is a great data source. In the past 10 years, on average, 6,000 PIs have been awarded each month! The total fund is approximately $30B each year.
If we look closely into one year (say 2021), we will find the number varies from month to month. It peaked in July, August and September (on average 10K+ grants per month). October and November are winter for grants.
We can help you compile a list of grant holders, including their email addresses, in an Excel format (screenshot below). This will make it easy for you to import them into your email marketing program and contact them. You may use this free tool to estimate the number.