Maxis is the first Malaysia telco to offer nano SIM card for future iPhone5 users starting from 24th September onwards. This tiny sim card measures 12.3×8.8 mm in size with a thickness of just 0.7mm has the same oomph of your previous micro SIM.
For only RM25, you can get it from the Maxis centres below. Other centres will follow suit in late September.
Taman Tun Dr. Ismail