I'm planning to do a lot of riding this spring/summer and a lot of it will be down the shore. I want to bring a spare helmet and jacket I have for females I may be meeting up with. My bike came with some kind of tie down strap (if I can find it) but I was never really able to figure out how to use it. I want a secure way to strap down a helmet and an extra jacket in case I need them. I rather not carry a backpack or anything. Any ideas? Thanks.