Have you considered a travel router? I have a Gli.net travel router, and that can connect to an existing WiFi network and then you can create your own lan behind that. You can even configure it to use a VPN service if your concerned about your traffic on the existing WiFi.
I checked them out, seems like a good product to have, however they're not sold in my country and import is getting expensive in itself. But imma keep a keen eye on this one! Thanks 👍
If get a cheap network adapter. Ubiquiti's Unifi is great for access points and they can be had cheap second hand, taken off of office buildings. Unfortunately they don't connect to third party access points as clients so there's probably no point getting one now. I'm running Unifi at several locations and they've been rock solid access points. One thing they are not good at is mesh/wireless bridge. It's easy to setup once you have cloud key, but its latency performance is far from great. In contrast, WDS connected OpenWrt manages consistently low wireless bridge. That's not what you care about but I'm just sharing a known con of Unifi.