Back in the old days (1880s-1910s), cycletourists would leave their hotel with instructions to forward their dunnage by rail c/o the next night's hotel. It was elegant touring for a more civilized age.
In addition to the old school backpacking bags that don't require racks,
there are the more modern saddlebags and handlebar bags, shown here sitting on racks but not requiring them.
And there are Old Man Mountain racks & the like for bikes that don't have rack eyelets.
Here's a wild and crazy idea: pack up two kits, and alternately UPS/USPS/FedEx them
Next Day to your destination second day hence.
