SPARCs in Space: The Cobham UT700 Leon3FT Processor (cpushack.com)

The CPUs are designed by Graisler Research in Sweden, who have decades of experience in space electronics and probably have thousands of CPUs currently orbiting the earth.

And yes, they have RISC-V versions but I don't think they have been battle proven as much:

https://www.gaisler.com/index.php/products/processors/noel-v

I do not know about commercially available, but the ESA has long selected the RISC-V NOEL-V[0] to succeed LEON in their space endeavors.

0. http://microelectronics.esa.int/riscv/rvws2022/index.php