You'll need to look under the plastic bumper cover to see what is there to brace from. Look were the bumper support mounts to see if you can build from there. You'll probably have to cut holes in the cover to access the mounts.
I built my first 1-wheel towing setup about 1974 for my RD350. The 1st one was a pipe the axle would fit thru welded to a plate that bolted to my trailer hitch, using the ball to hold it. Removed the front wheel, slid a piece of wood in the caliper with a bungee holding the lever, and put the axle in. Still had to tie the bars off & you could not back up worth a *#@^. But it worked, always removed the chain too.
The next, for a Yamaha 650 twin, was similar but used pieces from an oil drum for the front tire to rest in. Still removed the chain.
Never tried pulling one backwards. I think it would be easier on the bike & car to go foward.
Is there enough room to take the belt loose & tie it out of the way?
It would be easier if you can find some sort of hitch.