I want to get a good quality wireless clip-on microphone for my iPhone (not rubbish bluetooth). All wireless lavalier mics seem to have receivers which have a a TRS jack plug (Left+right). Whereas smartphones, including iPhones (or with headset adapter) have TRRS sockets (Left + right + mic). More on discussions.apple.com

It sounds like you're referring to lavalier microphones, often called lapel mics. They're indeed really useful for on-the-go setups. Brands vary, but it's the quality and functionality that you should prioritize. IMO, the key factors include sound quality, compatibility with devices, durability, and battery life. Also, wireless versions provide more mobility. A certain clip-on wireless microphone that I personally use has served me well with its excellent sound capture and comfortable clip. It’s wireless so moving around is easy, and its battery lasts a decent time, so I'd definitely recommend it, given its balance of quality and price. More on reddit.com

As I’m finally getting into video production, in large part using the iPhone as the main capture device, I recently got a lavalier microphone for better sound. I got the Sennheiser XS Lav USB-C, but probably the main point is that it’s USB-C with no additional audio interface involved. More on talk.macpowerusers.com

I would buy a Zoom H1 recorder. It has a slot for an SD card, and also a USB-C port. I haven’t tested it, but if you’re using something like GarageBand, you should in theory be able to use a USB-C (or USB-C to lightning) to load it into that. At the very least, you should be able to save the mp3 on your phone ETA: being a standalone recorder, it’ll allow you to use it where phones may not be particularly professional (recording a performance you’re putting on for example) and it’ll also let you record sectionals or ensembles. More on reddit.com