I can recommed the Plantower 5003 PM sensor. Plantower also has smaller ones, e.g. 7003 or A003 but we get the best (most accurate and stable) readings from the 5003 model.
We also experienced with more expensive ones e.g. from Sensirion but did not really measure a significant advantage compared to the Plantower.
Which circuit boards do you recommend that have high accuracy that can be ordered?