Sample 1: I have all data plus instrumental variables; Sample 2: I have all data but NOT the instrumental variables; What to do?

[Joro Kolev]

Good morning,

I am soliciting ideas of what you would do in the following situation:

I have two waves of a survey. The survey is not panel data, individuals are not being followed over time. The survey is repeated cross sections.

For the first wave of the survey I have all my variables of interest, plus some instrumental variables which I use in my IV estimation.

For the second wave of the survey, I have all my variables of interest, but I do not have anymore the instrumental variables.

I still want to carry out my IV regressions for the second wave of the survey. What would you do?