To say a few things about equipment, i went a somehow “modular/extendable” way:
as a base portable recorder, i have a Sony PCM-M10 alway with me. The integrated microphones are acceptable enough to capture interesting things that might come up.
I also carry a cheap contact mic, and sometimes a good old Lem DO21 (classic french radio tool).
For “planned” sessions, i use a pair of MKH8040 in ORTF configuration, going into a Sound Devices MixPre-D, going into the M10. The whole thing plus a tripod can be transported in a photographer’s rucksack, which allows to walk for a good while before attaining a spot.