I use this stuff: Acrylic Cement from tap Plastics. It's also sold under different names, including "Weld-On"
http://www.tapplastics.com/product/repa … cement/130
I used to work as a model maker 20 years ago, and this is the only stuff we used in our model shop. It's the best stuff you can get for plastics, however you need to be careful with it. It literally melts the plastic. If you get it on some surface it will etch the surface instantly.
To apply it, I use a syringe for precision. Since it flows like water, you only need to put a drop on the seam, and it flows on it's own to fill the gap

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To print or, 3D print, that is the question...
SD3 printer w/too many mods, Printrbot Simple Maker Ed., FormLabs Form 1+
AnyCubic Photon, Shining 3D EinScan-S & Atlas 3D scanners...
...and too much time on my hands.