Not sure if this is the right place to ask. I'm making an assumption that if I see something called "Flirc" it's supported here. If that's wrong, apologies in advance.
According to Flirc.tv there are only Pi 2 cases (as that's all that site sells).
ModMyPi is selling a Pi 3 case listed as "support[ing] the Raspberry Pi B+/2/3". In the Q&A section of that page, ModMyPi state it's not compatible with the Raspberry Pi 3 B+.
Looking at this photo the only component which comes into contact with the case would be the CPU. Comparing drawings of 3B and 3B+ the