Is it correct to say, "an example for this is . . .".?
Solution 1:
The correct preposition is "of". "Example for" is occasionally used in literature, but that is likely because of a typo or other mistake.
For proof, refer to the Ngram results:
Solution 2:
There are 319 British National Corpus citations for an example of this and only one for an example for this. We don't say for in British English.