If you don't mind some drilling, you could make a "hood pin" style hold down. I did that with some bolts and pins from our tractor supply store to hold down my kammback on my Neon.
I put bolt up through the bottom, with 2 nuts, one on top of the trunk lid and one below to set the height that I wanted for the hole I drilled through the bolt, don't go too big or you may compromise the strength of the bolt, then a simple clip pin.
Then all you have to do is pull the pin and you're done!