Any tips for finding niche-specific "influencers" from other countries?

First, I'd like to apologize for making my first ever Indie Hackers post a question. Ultimately, I'd like to give to this community more than I take. Nevertheless, I've been struggling with this question for weeks (and it's delaying my project), so I'm putting up the Bat Signal in the hopes that it helps me while also facilitating some discussion about this...

I'm working on a Web App and I'd like to feature specific "influencers" from other countries. I hate using that term, so another way of thinking about it would be a blogger/ social media personalities with an engaged following (big is great, but ENGAGED is key).

Ultimately, I want to network with these folks long term, while also providing them a platform to share their work and get compensated via sign-up referrals.

Here are some platforms I've used in the past, along with notes on why I'm having trouble leveraging them to solve this challenge:

1. Twitonomy - This is a really powerful (and free) tool for looking at Twitter accounts. If you've never played with it before, I'd recommend checking it out. My favorite thing is seeing how accounts interact with one another, which I think is pretty unique. Anyways, this tool is great but I'm having trouble accomplishing my goal. Maybe I'm just not using the right inputs, or thought process...

2. Buzzstream - This can be a pretty great tool, but personally I think it's a little over-hyped. When I was working as an agency, yes, it was a fantastic tool to keep everything organized by project, tag, etc. But when you're starting from scratch, I don't think it's that great because it doesn't really help with the discovery process. Which is probably why the same company launched Buzz Sumo...

3. Buzz Sumo - Again, great service here. But I'm having difficulty drilling down by niche and location. Also, I'd prefer not to have to pay for a service. Has anyone used the paid version of this, and is it worth it?

On a final note, I can't disclose the niche I'm working in but I don't think that matters too much. I can say it's in the health and wellness industry and is super popular-- nothing obscure.

Looking forward to hearing some thoughts. And if you have any questions about my normal process, or want to get a parallel discussion going, I'd love that too!