Another option would be to spin up a few VMs on various pay-per-use cloud providers, perhaps VMs in a couple of Azure regions, and test by pulling data from those. The variety of regions will rule out local traffic problems at the other end, the pay-by-hour/minute/second nature of such VMs would make it a cheap test to run. Especially if you can leave the VMs configured but stopped between tests and have no cost in that state, so you pay nothing most of the time but don't have to wait for provisioning & configuration each time.

Or if you have external servers for other uses, and/or have friends who do, you could use those instead of needing to spin up anything new.