Surface sensors are produced either as mineral insulated thermocouples or as mineral insulated resistance thermometers (Pt100, Pt1000). You may select a design. The contact plates are available as copper or stainless steel plates, at various sizes and thicknesses.
Thermocouples with contact plates welded onto them are a low-price alternative solution to mineral insulated thermocouples and resistance thermometers for surface temperature measurement. One of their benefits is a shorter/quicker response time, as the measuring tip is bare and directly welded on the contact plate.
The use of this sensor type requires a humidity-free surrounding. The sensor can easily be fixed with kapton tape (up to 370!C).