Templum Isidis sounds about right to me.
Iseum was the common name of the Temple of Isis in Rome, but it's possible to see some variations such as Isiacum although it may not be the temple itself.
Admittedly, it could depends on which epithets your local Isis have : Reginum could be a possible alternative.
Where does Reginum come from?
Where does Reginum come from?
The Gods had a lot of different epithets, which appeared in temples dedicated to them. For example, Rome had temples to Mars Ultor and Jupiter Optimus Maximus. Thus, the temple honors a certain aspect of the deity.