Just posted an auction on ebay for 11 Gibraltar tension rods with built in washers. I know they're not vintage but they will work will vintage drums like LUDWIG.

https://www.ebay.com/itm/11-Gibraltar-Tension-Rods-With-Built-In-Washers/264239468320?hash=item3d85e64f20:g:aiAAAOSw9bpcitTg