Use any search engine you want and type this phrase "quilting ruler storage bag pattern free". The key is going to be what size ruler(s) you want to transport I would consider a bag where the rulers are encased so they can't slip out and you have pockets to put smaller rulers in. A flat bottom will give you space for other needs. If you take a smaller sewing machine, you might want to add enough space for it too.
I haven't made one but will at some point in time. Lots of ideas here.
https://www.bing.com/images/search?q...1&disoverlay=1