They’re available on Amazon for a decent price. I’m not sure if the model I last referenced was including WWAN, but an FZ-55 mk1 was approximately $1k (USD). I think I paid right around $1380 for my FZ-55 mk1 and it included 4G LTE modem when it arrived. I set it up with a Consumer Cellular unlimited data line at $60 USD per month and it gets pretty decent signal in my living room. Oddly enough, perhaps due to tower loading, the bandwidth is around 50mbit download at home, and less everywhere else usually with stronger signal. It is a bit heavy, but it has a handle and fits snugly into the laptop sleeve of my backpack. Also, it has a touchscreen and even a stylus. Now I can be a volunteer police officer with my own equipment.
According to ChatGPT, the high speed data threshold for throttling is 35GB but it doesn’t cap like EIOTClub does. EIOTClub sim cards are data only prepaid sim cards which work fine. AT&T doesn’t provide IPv6 (neither did EIOTClub), but with tailscale setup as an exit node on a small VPS I still have (a 512MB one, nonetheless) that runs my ZNC bouncer and an exit node, I get IPv6 through tailscale. The only problem is, on the map, it thinks I’m in Las Vegas. That is the problem with exit nodes, but perhaps I can get IPv6 working on my local exit node. That said, be careful with a VPN with a WWAN modem, as when it switches connection, Tailscale will timeout momentarily if you use it with an exit-node.