I think the Parking Spot Haynes might be your best bet as I mentioned in another thread.

They are 100% mask required and compliance in my ~6 or so uses since this all got started.

They offer payment/reservations via the app so you can have a contactless experience on entry and exit.

On the shuttle they also have seats blocked for distancing and use the reduced seat count to say its "full" although because of the reduced number of people flying I have only been on a bus with maybe 3 people.

Not to mention Parking Spot Haynes is the closest lot I believe its like 1.3 miles from their gate to the Curb at Terminal C (shorter if you depart out of B and C).

Here is a photo of the inside of the bus with the distancing stuff.




Honestly, though if you are having this much concern over the parking lot shuttle, you might find lots of other "kinks" along the way that make you uncomfortable.

Boarding on airlines like AA are back to Pre-Covid groups, and even on Delta who was only boarding 10 at a time at one point things have gotten kind of relaxed.

The parking lot ride at least to me is the least concerning part of air travel right now, but YMMV.

Hope this is helpful.