carry handle is exactly the same as the KSG's and is available to purchase from Kel Tec's website. There is also a longer/extended aftermarket rail available for the KSG/KS7. https://www.hitechcc.com/product/HTC-105_KS7.html
The KSG did not feel flimsy to me. Sure, it's plasticky like a Glock but I expected that. I'm ambivalent about the handle vs. no handle.
I'd buy a KSG but they're more than double the price and I doubt that I'll "need" 14 rounds in a home invasion situation. I figure after 2 rounds any intruders will be horizontal or will have fled. I expect that I'll need to practice my drywall patching skills.