There are many that attend local meetups, alot are active in the biggerpockets forums, and BP has a tool that matches you to local agents. A good question to ask, to see if they truly are investor friendly, is how many investors they've worked with. Its better than just asking if they work with investors, because of course they'll say yes. Other than that, having a good education in real estate investing makes it easier to vet them and having a clear understanding of what you want out of an agent, makes it easier to set expectations. I learned this from the BP rookie podcast.
Great question! You asked how to find an investor friendly real estate agent.
Ideally, you want to find one in the area you are interested in investing with a teacher's heart and personal investing experience of their own.
You can find these investor friendly real estate agents by talking to other investors, local real estate investor meetups locally, local property managers, look to see who is listing investment real estate frequently in the area you are interested, and local Facebook groups for real estate investors.
Talk to a few and share your goals and see which seem to be the most responsive and knowledgable for your specific goals.