Yes, replacement lower legs are available for the 2021-2023 SID SL C1. The lower legs are compatible with both C1 and D1 chassis, so they have a usable range of 80-110mm, but the C1 CSU has a limit of 100mm. 110mm of travel is not achievable with SID SL C1.
11.4018.091.092 FORK LOWER LEG - (WHITE DECALS INCLUDED) 29 15X110 BOOST™ BLUE CRUSH ULTIMATE 80-110mm - SID SL C1-D1 (2021-2026)
11.4018.091.093 FORK LOWER LEG - (WHITE DECALS INCLUDED) 29 15X110 BOOST™ GLOSS BLACK ULTIMATE 80-110mm - SID SL C1-D1 (2021-2026)
11.4018.091.094 FORK LOWER LEG - (DECALS INCLUDED) 29 15X110 BOOST™ DIFFUSION BLACK SELECT/SELECT+ 80-110mm - SID SL C1-D1 (2021-2026)
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