What do you mean by “high risk”? If it is someone with a medical condition that is trying to avoid Covid 19, there are plenty of options. Just use google. You will probably get results of companies like Wheels Up (formerly Delta Private Jets), XO Jets, Jet Smarter, Jet Suite, etc. You could also just call the FBO of your closest airport and ask them for a referral to someone on the General Aviation side of the field.
If the “high risk” person has a medical condition that in itself is life threatening. And, they need special transportation due to the need for treatment, you could look up one of the various Angel Flight organizations. These are generally individually owned aircraft.
If the person needs special treatment during the flight. And, costs are covered by insurance. Or, cost is not a factor, you could contact a local medical transport company. Many operate both fixed-wing and rotary-wing aircraft that can make the trip.