I’ve got a couple of these:
http://Bike Racks Stands, Bike Fork Mount Quick Release Roof Bike Rack Bicycle Fork Bracket Frame MTB Carriers for Car https://amzn.eu/d/gaA78Zx
That bolt to T-bolts on a roof bar (or whatever else you might want) and I just use the rear wheel sucker from my off-brand sea sucker copy to keep the back wheel in place. but you could put a second bar there and bolt on something with a V-channel and a strap.
In fact this might be a better call if you already have roof bars as it includes a rear wheel bracket:
http://Bike Fork Mount, Parking Rack with Front Fork Bracket and Rear Wheel Mount Complete Set, Bike Car Roof Rack Carrier, Quick Release Thru Axle Fitments, Bike Block Mount for Travel Transporting Bicycle https://amzn.eu/d/5YhppgY
New car coming next week with annoying flush mount rails means I’ll need to look at alternative roof bars, so might be back to the Suction mounted rack for a while, but I’ve never quite trusted it for more than a shortish journey (despite no evidence of failure so far).