There are many freelance type things that aren't strictly MSing, but are probably in the same basic genre.
Merchandising. Many IC jobs out there, and reset crews are always hiring where you are a W2 employee.
Facility audits. All the gas station audits really aren't MSing, although a small component is.
Product recalls/retrievals. Sign up with RQA and Sedgwick.
Focus groups. When you can find them.
Photo/shelf/product audits. Some decent jobs out there on Field Agent, Observa, ProxyPics, iVueit, etc
Delivery. Roadie, Spark, Instacart, Shipt, Doordash, UberEats, and many others
I used to do a lot of MS jobs, but not anymore. I made 2K/month on average in 2024. I did a total of 10 MS jobs, all were post office shops before the new company assumed the contract. Most of the jobs that I did fit within the list above.