All 6804 and 61804 bearings are the same size.
You might also see bearings marked 7804 or 71804. These will be the same size as well but angular contact bearings. You might be able to use these as well if your cranks allow you to set preload.
Ok, so correction.I just noticed earlier reference to the FSA cranks having a 19mm spindle, which doesn’t gibe with the standard 6804 bearing, which is confusing. I googled MR129, the other marking on the beaaring, and it equates to an FSA bearing with a tapered inner race.
https://www.kineticbikebearings.com/mr129.html
Note in the above reference to the MR129 being specific to the nondrive side, meaning you might need a different size for the drive side.