Are you using the handle? Yes it is a bit high.
Anything you try to attach is likely to stop the boot closing or get caught between the lid and the sill.
You could just try a few things like a piece of nylon rope, luggage elastic or something.
Otherwise, improvise something from whatever you have lying about and clamp it to the handle using a cheap clamp from home bargains, poundstrecher or b&m.
Can't think of anything else at the moment.