Text option in choice and checkbox questions

In choice and checkbox questions, I would often like to include an option which allows the user to enter arbitrary text.

e.g. for a choice "Where did you hear about us?" with the options "Friends" and "Colleagues", I'd also like to have an option "Other" which allows users to enter arbitrary text.

A workaround is to insert a conditional section and a text input widget, but that takes up more space than what I'm suggesting, which gives the impression of a form that's longer than it actually is, and thus discourages respondents. It is also removed from the context of the previous question, which then has to be reestablished.