Here is a nice reproduction Mud Flap for late ATC90 and early ATC110 models. Also can be fitted to ATC185S but are not as long down the side, (ATC185S has 3 side bolts, these have 2). Previously near impossible to find we had these remade. Sold per each but are reversible so if you only need one you are covered but if you want left and right just order 2.
Suits ATC90 77-78, ATC110 79-82 (plus other models as mentioned above)