Any apps or good ways to find remote raids to join?

I’m in a kinda rural area, I’ve only ever had one raid where a random person joined so I can’t do any 5 star or mega raids without travelling 4+ hours. Is there any way i can join a raid with other people from where I am without being friends with them?

Reshiram is one of my favourite Pokémon and I’d like to be able to get it before it goes away