Yes, replacement CSUs are available for the 2021-2023 SID (35MM) C1.
11.4018.090.027 FORK CSU - DEBONAIR 29 BOOST™ 44 OFF-SET ALUMINUM TAPER BLACK ANO SID (35MM) ULTIMATE C1 100-120MM (2021-2023)
11.4018.090.028 FORK CSU - DEBONAIR 29 BOOST™ 44 OFF-SET ALUMINUM TAPER DIFFUSION DIFFUSION BLACK SID (35MM) SELECT/SELECT+ C1 100-120MM (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