You won't find any commercially available that meet the hillclimb required coverage. Cheapest route - just use one in the pits at each race as there are usually plenty floating around. If you want to measure some and see how they have their lift handles set up you could build your own. Some hold better than others though, so see how they fit for your bumper and make sure it lifts high enough and has enough clearance it to not stuff the flap into the track. Everybody is usually very friendly about sharing, so don't feel awkward asking if you can't come up with one. Good luck at the races.