Most of what I know about creators finding sponsor deals, I learned from Noa Bucko... the 2nd most I learned from Justin Moore.
Justin has his "10k Challenge" a couple of times a year, where he takes 4 days to teach influencers/influencer managers how to find sponsors. (it's recorded as well, for ppl who can't make it live)
The cost? $47. (he sells it this cheaply because he sells coaching at the end)
Either way, it's an amazing program for $47... you can get info here if you're trying to get better at finding deals.