When I'm going down the highway and go to flip on my blinkers, they either don't react, or they blink VERY slowly. However, in town <(50 mph) they work perfectly.

Also, if I pull in the clutch and coast it on the highway, the blinkers work fine.

Does anyone know a good fix for this issue?

I don't have a ton of motorcycle experience, but my electrics mucking about makes me think bad ground.

I would guess at high speeds something is vibrating its ground loose, or coming in contact with metal somewhere and that's sucking away your power giving you poorly working signals.  With the clutch in, perhaps things settle down enough where you have a solid connection again?

Chasing bad grounds can be wholly unfun.  Or not bad at all. Good luck. 

I'd open up the headlight, and find the turn signal wires.  I'd unplug the ground, and using another piece of electrical wire just ground it to some metal temporarily using electrical tape, and see if that solves your issues.  If so, either solidly ground the blinkers somewhere else or go find where your metal isn't happy with life.