A Center Controller reported an aircraft at low altitude deviated for weather into the adjacent Center's airspace. The Controller did not have access to minimum IFR Altitude information for that facility's airspace.

Narrative

Aircraft X was enroute to ZZZ airport at 13000 ft. There was a line of moderate to extreme precipitation with a few gaps in the weather starting from southwest of ZZZ1 to north of ZZZ2. I was attempting to vector Aircraft X thru the gaps just southwest of ZZZ1. As the pilot got closer to the weather; he wanted to deviate around the weather on his own. This caused Aircraft X to fly into ZZZZ Center airspace. Terrain information is not depicted on the radar within their airspace. I called ZZZZ Center and asked if they can give me the Minimum IFR altitude in that area. She said 'No IFR.' I understood that as they don't have any ZZZ [Center] information in their airspace; but in hindsight; it could've been mistaken as she doesn't have any IFR aircraft in that area. I told Aircraft X I can't give him terrain guidance/information in that area. This could've been problematic; especially since he had trouble holding altitude flying thru the weather. I recommend a procedure be implemented for low flying aircraft that need to deviate into ZZZZ1/ZZZZ Center. Having knowledge of the Minimum safe/IFR altitude in their airspace will allow us to provide terrain guidance in an abnormal situation such as deviating or emergency aircraft.