Hammond Typewriter parts are in precious short supply. While efforts have been undertaken to reproduce some of these components, they’re not quite ready for wider use. Eventually you’ll be able to come here and find parts and supplies, but until then please check out these links.
Removable of the front roller on a Hammond is quite easy but removable of the back roller should never be undertaken unless absolutely necessary. The carriage brackets are brittle and can snap with the slightest pressure, which is needed to remove that rear-roller.
However, the front roller can be removed and resurfaced. The best company for that is J.J. Short Associates, Inc.
Parts and Shuttles
The best place to find parts is via eBay. Occasionally, The AntiKey Chop will have harder to find parts and shuttles.