Push pin style clips.  An assortent of 6, 8, 10, 12 mm diameter posts.  Can easily be adusted during slicing by scaling x/y or z axis for inbetween customized sizing.  Probably can print with any plastic but something like petg will provide more flexibility and durability than straight PLA.  Print with high infill for strength.  Name has sizing - diameter/length.  Inner and outer should match sizes.   Printed standing on big end with no support worked best for me.