In the table below, I present a near-complete set of Dutch words that consist of tautonyms to which have been added a single letter, either in front, in the middle, or behind. A few of the words (italicized) can be used either in the first or third column. Koekoek and wouwouw are bird names.
Corstius, Hugo Brandt
"Enlarging Dutch Tautonyms,"
Word Ways: Vol. 39
, Article 20.
Available at: https://digitalcommons.butler.edu/wordways/vol39/iss1/20