The best external recruitment source would be temporary agencies.
Explanation:
A temporary agency works on finding and keeping employees. Companies tend to hire this external recruitment source in order to get temporary workers.
In this case, this organization's best option for a short-term labor shortage like this, would be to get help from a temporary agency because it is quicker, it's a temporary filling and there is no time for a screening process.
Essentially, these guidelines are there to protect the participants from harm/distress. Therefore, they are safeguarding the wellbeing of the participants.
