I was looking for a case for my Blade SR 120 and found this EXI 250 helicopter case that was made for a TREX 250.  It seems to fit the 120SR very well too. It also has room for a transmitter (DX6i), charter, batteries, the works. It measures 488mm x 228mm x 241mm.  Cost was about $20 with free shipping from xheli.com, search for “EXI 250 Aluminum Carrying Case”

Here’s the 120SR fitting snug with my DX6i.

Here it is with my Blade mSR.  The mSR fits pretty snug in the transmitter cut out.