This docker image starts up snmpsim.
The UDP port 161 should be mapped to the desired SNMP port.
By default this image contains an snmpwalk from demo.snmplabs.com under community name demo.
To use your own snmpwalks you should mount a folder with snmpwalks like this:
docker run -v /somewhere/with/snmpwalks:/usr/share/snmpsim/data \
-p 161:161/udp \
tandrup/snmpsim
The filename determines the SNMP community name.