There are two brake line supports that secure the feed to the second brake caliper - they simply unclip out of the fender, and back into the new one.
The other retainer, which secures the primary feed from the master cyclinder down to the first calipers in the circuit is indeed, as you rightly suggested, riveted in. I believe new fenders come with that already attached as cannot see a seperate part no. for it.
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