If you have to travel light, want to use your Iphone as a recorder and have a budget of around 200 euro, I have to agree with Ruff-Leg for a small Rode mic compatible with an Iphone. Any shotgun will cost you more than you would like to spend. I think you should get de best small Rode mic compatible with an Iphone you can get. Think about a good compatible deadcat and why not a small handle to put the mic. It's gonna be waaayyyy more comfortable AND you should have better aiming and sound! If you like used item, in Canada there's A LOT of small Rode mic on Facebook marketplace.
For the price, the other option could be to ditch the Iphone and get a recorder with integrated mic. Zoom H1n with a deadcat fit your budget and get a lot of good reviews. For your budget, you could check on Facebook marketplace for a better recorder. I would skip the Zoom H4n to get directly for the Zoome H5.
That being said, if your backpacking trip isn't bird oriented, the Rode mic seems to be a better solution. Less weight, less space and a ton of fun!