Hachiouji-shi,
Until someone comes along with the answer you're looking for, it's a pretty fair estimate that on
pre-super critical winged aircraft, Mcrit is approximately equal to your Climb Mach No., or your Long Range Cruise Mach No. minus 0.02 or 0.03
Just 'ball park' figures to keep you going until the exact answer comes along. Given the large number of B737 models and their derivatives, stand by for a lot of different answers.
Regards,
Old Smokey