Yes, looking for a “bridge” for the first 30 days before my employer insurance kicks in. Relocating to the US.
OK, if you want annual multi-trip emergency medical coverage anyway, then Bupa Global is still a good option. It typically costs about 100 British pounds. The annual plan provides emergency medical coverage for up to one month per trip, so that should be just enough. I cannot find any reason why it wouldn't cover your first month in the United States, but please check the fine print in the policy document. You can buy a one month single trip plan, but it's basically the same price.
I've done some spot checks of other plans, but they've got some defects and at least aren't much less expensive.
....But shouldn't your employer be covering this period also?