I am all for DIY. That said, the only way I see it totally possible is that you will have to do some splicing and soldering. However, a big consideration is that by mixing and matching, you may also find the color hues are kinda off.
Also, here's something from Steve Housden of "SIK Baggers"
"You have various turn signals that will not all blink at the same time. This happens mainly when you mix brands and honestly, sometimes it can happen when using the same brands. Nothing you do will ever get this to line out. ALL LEDs have a "driver" in them...similar to a ballast. Even though all of the turn signals are getting the exact same information at the same time, doesn't mean the driver is taking that information and making them blink at the same time or even at the same rate, causing your turn signals to be off from each other. Also, note light systems like CIRO that have the "light strike" technology built in (has preset flash patterns you can choose from via their app) this will also make things wanky when mixing with other brands."
Some of our members have reported no issues with mixing and matching though. YMMV.
There are connectors and harnesses listed on pages for Ciro3D and Custom Dynamics. Those may be a good start as they can connect directly to the harness under your seat and then you could 'connectorize' the lights you are adding. Personally, if not going with a complete solution from a reliable source like Ciro or Custom Dynamics, I would at a minimum
, buy a plug-n-play harness connector from the two mentioned above as to not splice into the main harness for the main lighting. (Safety first!)
Alrighty, so I have used mostly the Plug-n-Play cables from Custom Dynamics. They really make it easy.
When I needed to modify the cable, I have used the following connectors for my light projects: