Your best bet today if you don't want to stay with the Turbomeca is Soloy's SD1 conversion kit using a Silver 600A-3A. Find out what the 1B will cost to overhaul and compare with the Soloy total kit price of $401,000.00.
It makes even more sense if you were to upgrade the helicopter to BA configuration at the same time. This engine in a BA runs rings round the standard ship at any temp. and altitude.