An interesting question, as I'm about to tackle the same issue on a side mounted lock of a 1979 m/f CB400N, key missing, but unlocked...I've done them before, but so long ago .

 

Pick it if you can or drill it out.

Since it is off the bike I would suggest doing a walk in at a small lock smith shop. Cash transaction.

 

can probably be picked easily with a rake type pick

 

Time for fiddling with the side lock on my CB400N was over 1 hour ago!.
Pop marked 2mm above the circular barrel on the rectangular surface.
Loaded a very sharp 4.2mm left hand drill.
Drilled all the tumblers out, even though it went through the wall of the lock, it did not graze the frame (this time).
Once drilled, I turned the barrel anti-clockwise to line up the grub screw to the 12 o'clock position, out it came with a little shake...