Vox Legi-Pattern Arbites Combat Shotgun: class basic; range 30m; RoF S/2/-; damage 1d10+9 I; Pen 0; clip 14; reload 2 full; reliable, scatter
Also, it is reinforced to allow it to be used as a club in melee.
Given that it takes a while to reload, I'd recommend having a fire selector installed as soon as possible - not necessarily to allow yourself to switch between different types of ammo, though that is a bonus, but just so that you can load three clips at once.
Finally, given how much you like the electro-flail, I thought I should offer up the neural whip for your consideration. It has the same properties (shocking and flexible), has a reach of 3m, and only requires one hand to use. The downsides are that it is slightly more expensive (500 thrones as opposed to 375) and deals one less damage per hit (1d10+1 instead of 1d10+2).