You can also form them out of sheet styrene, heat-formed (hot water) around a form of suitable diameter, or look for any number of cheap, thin metal cylindrical forms that come from a surprising number of ordinary items and "requisition" the one of your choice.
**SPECIAL CAUTION! As some of these items are attached to or part of household items, be certain spouse is not watching when "requisition" takes place. Always better to ask forgiveness than permission, Grasshopper. :mrgreen: