Agree with Robow, if you are where there are trees that you could use for a hammock, you should be able to support a tarp.
I have bought cheap poles, then cut the segments to shorter lengths to meet my needs. I have a trekking pole style tent that needs two poles, I cut longer poles down so that the poles will fold up short enough for a front pannier.
There was a recent thread on shelters and sleeping systems, there might be ideas there.
https://m.bikeforums.net/showthread.php?p=22431696