Yes, replacement C1 lower legs are available for the 2021-2023 SID (35MM) C1. Lower legs used in the D-generation of the SID 35MM are not compatible with the C1 chassis.
11.4018.091.032 FORK LOWER LEG - (FOIL DECALS INCLUDED) 29 15X110 BOOST™ BLUE -SID (35MM) ULTIMATE 100-120MM C1 (2021-2023)
11.4018.091.033 FORK LOWER LEG - (FOIL DECALS INCLUDED) 29 15X110 BOOST™ GLOSS BLACK -SID (35MM) ULTIMATE 100-120MM C1 (2021-2023)
11.4018.091.034 FORK LOWER LEG - (DECALS INCLUDED) 29 15X110 BOOST™ DIFFUSION BLACK - SID SID (35MM) SELECT/SELECT+ 100-120MM C1 (2021-2023)
RockShox service kits and spare parts are best obtained through your local shop or dealer. See our dealer locator, below, to find a dealer near you. If no one is currently listed near you, then please search for local shops via your preferred web browser.
https://www.sram.com/en/dealer-locator
Manuals and additional information about RockShox and SRAM components can be found at our service site, linked below.
https://www.sram.com/en/service
Further questions?
Reach out to Rider Support by Asking A Question at the link below.
https://www.sram.com/en/rockshox/campaigns/rockshox-rider-support