To confirm, Plan F = Plan G + deductible. Coverage is set by Medicare but prices vary all over the map based on your location, age, gender, tobacco use, how you're rated (see below), and the insurer. In my case, the range of costs for Plan F is $157-$464.
Suggestion to start at
https://www.medicare.gov/supplements-other-insurance/whats-medicare-supplement-insurance-medigap/medigap-costs and then go to 'Find a Medigap Policy' near the bottom of the page. Depending where you live, you may see a plethora of policies. You will notice there are various schemes used to price the policies such as Community-rated (also called “no age-rated”), Issue-age-rated (also called “entry age-rated”), or Attained-age-rated. After you enter your location, age, etc., you will see more details about these options.