Right at the start of the Greenway in Sallins is this bike hire and repair shop and a cafe. The owner is very helpful and very knowledgeable about all things associated with cycling on the Grand Canal. See also https://www.grandcanalgreenwaybikehire.ie/about/

With stores in Naas, Lucan and Dublin, Wheelworx can provide top class maintenance, no hire though.

Cahill Cycles has provided cycling services in Naas since 1947. They can provide all your parts and servicing needs . No hire though.

Patrick A Fleming is in Naas and will provide maintenance services, no hire though.