EZPZ! Look here:
Parking Brake Strut Levers 11" Rear Drum Fits 65-70 Charger Challenger Mopar GTX | eBay
UGLY URL, but these work very well for us here! eBay has a number of vendors selling these. I have some originals, which were bent by the former owner when he hastily slapped the rear wheel assembly together to sell the car (Our 1966 green rust-bubble) I suspect these are all slung out of some chinese plant, but they're adequate.
More of the same:
https://www.classicindustries.com/p...zfjwJWrzc7jpmFC46tsPdkJe9M-kLBlOM7xpAHoyIEbUE
Now, you state "I have changed all the brakes from drums to disc." and I wonder if you mean BOTH front wheels, or front AND rear? If the latter, you should get whatever is recommended in the kit you used for that. Do you have a big enough Master Cylinder to drive however many discs you have? I hope so..... For 4 discs, a booster driven setup becomes more necessary. I wouldn't do it so, but some folks sleep better I suppose, with discs all around.