Backpack, or front bags. My bike was pretty short and the backpack was a problem so I got a really cheap Schwinn branded bag/basket from Walmart. It's a nylon bag that hangs from a loop of plastic much like a basketball net or wastebasket liner. I think it wouldn't have worked well with a threadless headset but with the long quill it was great.
If it's a diamond frame you can get a frame bag but my bike at the time was a step-through.
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Genesis 49:16-17