There are TPMS available for trailers as an aftermarket add on, I use one made by TST.
Trailer tires are a frequent topic of disdain and heated discussions on RV forums. I avoid them whenever possible and use either P or LT tires when a suitable weight rating and size is available. However there are those who disagree and believe ST tires are the best. Often with smaller trailers there’s not many choices and ST will be the only choice. There are still quality differences within the ST tire brands, and trailer builders tend to use the cheapest tire available. If tire choices are of interest then some reading on RV forums would yield some recommendations.