Sure connect sealed butt splices
Same thing in quick connect connectors
Scroll around on the linked pages and look for the sure connect sealed connectors. Those are the ones that solder and shrink in one step. A heat gun will do the job too, they have a 275 F melting point.
Click on the arrows beside the page number (it's in the bar at the top of the page), on the mcmaster carr site and you can browse through the catalog...it's about 3600 pages of cool stuff you probably never knew even existed.
I'm sure there are other , better suppliers, cheaper too, I like Mc Master Carr because they are quick to ship, and the quality is always top notch.