You can buy replacements     check with Kraft Car Quest  in Exeter  or similar     ask for 67 impala    don't confuse them with Pontiac

.....since you had a horn issue in the column, and now this too, I think you just need to pull off the steering wheel and clean the mech there. It's all just abit dirty and not connecting from not being used for awhile. The signal cam can just be sprayed with a good penetrating oil like " Move It " made by Lloyds, WD40 is junk. Spray it , move the signal lever up and down a few times and I bet your signals will work fine. I doubt anything is broken there but you'll see easily enough if something is. The lever should cancel after the wheel is turned back to center after making the turn.

your canciling cam may be broken. A common problem as it is made of plastic.

 A cam repair kit approximately $18.00. Can confirm cost in AM

 

Dale @ NOS

1-800-667-6200