is it possible to connect a trickle charger to the heated clothing harness that's connected to the battery? Only this seems to be more accessible than the battery charging harness which I can't see on my 2014 FLHTK.
Or is there an easy way of accessing the battery charging harness?

 

You should be able to access the pig-tail for the battery tender with out much of a problem. If it was routed incorrectly for whatever reason when you took possession of the bike, then just remove the seat and side panels and re-route it to a more convenient location. Mine comes out of one of the holes in the frame plate just behind the rear cylinder head and over the transmission on the FLHX.

 

It is possible provided the connections are compatible. What you should keep in mind is that should something go awry with the charger the clothing harness fuse is a higher amp than the battery tender harness.

Like Know Better says, find or install the harness for the tender would be what I'd do.

 

I use the factory installed battery charging harness on my 2014 FLHTK for the battery tender plus and my heated jacket liner. Works fine for me.