You do have plenty of options when it comes to NCNG in On3/30. A prime
example is the Bachmann flatcars, they are quite close in size to NCNG
flats. Originally these cars would have been Carter Bros 24' flats, as
the NCNG wore them out they were rebuilt to be 25' long, if you
measure, your Bachmann flats are the right length and "close enough"
for some quick easy flats. To top that off, the Fruit Cars if I
remember correctly are just built on top of flats themselves. Some
hunting on ebay will find you plastic kits for San Francisco Cable
Cars in O which can be kitbashed into fairly reasonable Calhoun cars.
As for locomotives, if you are crafty you can turn a Bachmann 2-6-0
into a reasonable model of #2, I would replace the tender however with
the tender from the new 4-4-0, the reason being that the 4-4-0 tender
appears to be a stock Baldwin tender the same as would be used on #1,
2, 3 and 5 in later years. Of course you have the Boxcars from
Foothill Model Works as well as the trucks and hardware you'd need for
your Bachmann flats.
So you see, if you get creative there are a lot of pieces of NCNG
equipment that can be built quickly and on the cheap.