You should be able to use bandwidthScan.0 = 1.3.6.1.4.1.161.19.3.2.1.131.0
From the MIB:
"Bandwidth values for frequency scanning used by MIMO SMs only. When setting use a comma delimited list of bandwidths. For example: 10, 20"
You may also want to follow that change with radioBandScanConfig.0 = 1.3.6.1.4.1.161.19.3.2.1.133.0 which can be set to 0=instant, 1=delayed, 2=applyChanges.