When we need a central dowel for support (especially when traveling with a cake), we take a dowel rod, sharpen it, and hammer it through the cake and into the cake base. Some people use them as supports for tiered cakes also although we usually use hollow plastic supports or bubble tea straws.
(Amazon Description): Wooden Dowels Set of 12. Cut the length of the support pegs you require. Push into cake, between plates for extra support. Dowels measure approximately 12 x 1/4 inch. I prefer to use sharp pruning sheers for an easy and clean cut.