One side quest, "A Good Scrub," in *Kingdom Come: Deliverance 2* opens the door to a series of bathhouse-related quests, one of which requires you to find a flea-infested item for Betty. Here's how to locate it.
Finding Something Infested with Fleas
Starting "A Good Scrub"
Begin by speaking to the innkeeper in Kuttenberg about work. This will lead you to Betty, the bathhouse owner, located in the southeast part of the city. Accept her offer of work, which involves finding Matsek in Grund. Matsek is hesitant to be seen with the potential bathhouse employees, so discreetly approach him in the courtyard where he's waiting with three women. Speak to them, mention Betty, and escort them back to the city.

Promoting the Bathhouse
After bringing the women back, help Betty advertise the bathhouse. This involves creating a sales pitch with her and then shouting it out in the grain market, horse market, vintners’ street, and merchants’ street. Remember, this needs to be done during the day.
Cleaning and Inspection
Clean the bathhouse before the alderman's inspection. Failure to do so quickly enough will result in the bathhouse being shut down, preventing you from progressing to the next stage of the quest, "Ill Repute."
"Ill Repute" and the Flea-Infested Item
Once the inspection is passed, speak to Betty about remaining issues. To help her out, you'll need to encourage Councillor Naaz to leave a competing bathhouse. This involves discovering his dislikes by talking to Meaty Mary, Katcha, and Little Lida. You'll need chamomile brew (for the wine cask on the second floor), and potentially a noblewoman's dress (to get information from Lida), or you can steal fragrant oils from a cabinet on the third floor.
Katcha mentions the bathhouse's past flea problem. To find the flea-infested item, head to Kuttenberg's east gate. There, you'll find a beggar camp; search their sacks for a flea-infested blanket.

Return to the bathhouse and discreetly place the fleas in Councillor Naaz's laundry basket (and a clean basket, if possible). Note that completing this task is optional; successfully completing one of the three tasks is enough to progress the quest.
Kingdom Come: Deliverance 2 is available now on PlayStation, Xbox, and PC.