I've been paying 5$ for mine. They are thick rubber, I get them at ace hardware. They work pretty well, They are sold at pool supply stores also. I'll try to get some pictures. Water dyke, sand dyke, waterever they are called....
We can get them for you if you are interested they come in 4' lengths so you can handle them easily. You could also cut them down if you like, let me know if I can help.
FYI by mixing Vermiculite into the sand which is “ a naturally occurring mineral composed of shiny flakes", you can find at garden centers, it will make the sand bag less heavy but not effect how it works.