Anonymous Insights and Freeman both do hotel shops. Be aware that the reports are lengthy and detailed, the pay is low for the amount of work, they usually have you charge the room to your credit card and then within a few days (or weeks) the client reverses the charges and unless you are lucky you won't find shops that correspond to a trip you might have planned. They work when you plan your trip around the hotels. These generally also are not particularly wonderful hotels, though generally they are clean and safe.
There have been casino shops posted on the job board here. I have never done one. I know with one company if you do a casino shop you are not allowed to gamble at that location or any other one in town, yet with others they will reimburse you. Go figure.