Live in the US. Traveling to England end of September. What is a good insurance that would cover my expenses if the Covid or another virus appears? If there are restrictions such as shots, I may not chose to travel.
For travel insurance information: on this Rick Steves' site - go to "travel tips" then click on "trip planning"
There is not a simple answer to your question. Travel insurance is not generic. You might look at Insuremytrip.com and or squaremouth.com. You can compare policies. Also read the fine print a couple of times. Not all policies will cover Covid problems. You probably are looking for some form of trip interruption and perhaps medical evacuation insurance. Good luck.
Not sure what you mean by restrictions. Right now there are no mandatory vaccinations. But who knows what the future holds? Are you suggesting that you might not travel if there is a mandate. I doubt if insurance would cover that.
I'm no expert, but I think two of the scenarios you're suggesting are very unlikely.
(1) Requiring proof of vaccination for travel or entry into the UK is unlikely in the foreseeable future.
(2) It's unlikely that any travel insurance would cover your non-reimbursable expenses (air fare, prepaid hotel etc.) if you chose not to travel because you didn't want to comply with a requirement such as being vaccinated or having a negative Covid test.
As others have commented, there's a section on the other side of this forum with lots of info on travel insurance.
Check previous posts using the search feature. Insurance is talked about daily.
https://search.ricksteves.com/?button=&date_range=6m&filter=Travel+Forum&query=Travel+insurance&utf8=%E2%9C%93
Allianz Travel Insurance has a Covid rider so read it carefully to find out if it will fit your needs. But they will not cover you if you cancel because you fear getting Covid.
https://www.allianztravelinsurance.com/