Are you just looking to find the OIDs for monitoring PSU and fans?
For the nexus you should be able to use:
1.3.6.1.4.1.9.9.117.1.4.1.1.1 - fans
1.3.6.1.4.1.9.9.117.1.1.2.1.2 - psu
I find this site much more helpful
Cisco SNMP Object Navigator
If you snmpwalk those OIDs you should be able to find the identifier for each instance if there are multiple PSU and fan modules.