Your best bet is to set up standard searches on eBay for each item you are looking for. These are all generic and not specific to the 113.
The dealer directories were updated on a quarterly basis, so keep an eye on the dates if you feel the need to be consistent with the year of the car.
I am not sure about the update frequency on the map books, there are at least three major regional books, Americas/Africa/ Australia, Europe, Germany. Not sure if there are others.
There are two types of map books, one that is the size of the owner's manual that would fit in the plastic pouch usually stored in the spare tire. And a smaller one that would be stored in the glove box.
The service record booklet - but there are two types an early version up to 1965 (not sure of the exact date) with a silhouette of a 111 coupe and the later version with a silhouette of a 108/109 sedan. These are relatively easy to find, but they will almost always be written in. I have not been successful in finding a completely clear one.
What I did to assemble a full set was at times to buy a set from a sedan or some such just to get a seat belt book, or the map, etc. I did end up with odds and ends, but was successful in getting all the items, even a blank dealer's welcome letter form.
