Preiser....

Dear Neil,

Preiser appear to have "family" and "railway workers/train crew" from both China and Japan...

...may be a usable figure-kitbash starting point?

(Google will get you the links, Walthers is listed as a supplier) 

Happy Modelling,

Aim to Improve,

Prof Klyzlr

Unsure Commercially

You may be able to make your own. There's a program called  MakeHuman where you can build 3D models of people, including making poses for them. Then, if you take the file to Shapeways (or similar), you may be able to print your own figures.

What about armour models?

Some of them will be 1:48, and Japanese WWII is a common subject, no?

???

Do you have any field/RR works from that era?

I'm thinking you might need do a bit of surgery to get exactly what you want - along with paint colors and shading. 

Would the field workers be wearing the conical shaped hat that Hollywood seemed to like using to designate someone as Asian? That would be a quick print job, or you might even make it with paper and a small punch. 

I think at least half your battle would be won if  you had figures with the right clothing for the era/job/ethnicity. 

Good ideas!

 
Here are a couple examples of Japanese cane workers around the 1890’s. 
 

I found Makehuman but need to spend some time with it. Shapeways maybe a good bet. 

Hats, masks, and coloration

I think those are going to be the things that make your figures distinctive, at least in the fields. I have never seen hats that looked like that before. Having masks that hide most of the face will likely simplify that as well. 

The rest is just finding the right paint colors for a variety of skin tone shades. 

One possibility

Wyrd Miniatures.

These packs are worth a look. They are in 32mm gaming scale, but in heroic scale so you wouldn't notice the difference at O scale.

The trouble is the lack of individual figure packs, and the fact that the designers go right over the top with the steampunk design cues, so you may need to buy multiple packs to find enough figures, and will have leftovers.

Unless, of course, your research uncovers credible evidence of steamborg, clockbots, zombies, various coloured demons and the odd Eastern dragon helping tame the West.

No.

Japanese is largely an also-ran in the more common military modelling scales, and nothing is terribly common in 1/48 these days except for horrifically expensive resin kits; and WW2 soldiers don't really look like 19th century immigrant fettlers.

3D printing

Neil, you mentioned shapeways, but I thought you had a form labs printer, that should provide good detail to print your own.

Choices choices and lack of choices.

Thanks guys.
 

Jeff, I have been trying a little carving (again) but my techniques for F scale (1:20.3) don’t translate well to 1:48. 

Jim - no 3d printer (yet) but my birthday is only a couple weeks away. Honestly I don’t know if I have the place to set it up or the time to design figures. One the other hand, Shadowbeast has pointed out that even wargame figures are pretty expensive and many wouldn’t fit anyway. 
 

A Hawaiian, now in the Bay Area, has a Shapeways site that has some really nice figures. If I could talk Richard into doing more period pieces it may be a good start but these are really works of art. 
 

ScaleHumans
 

The journey continues. 

You might try looking for

You might try looking for some Vietnam War era fieldworkers in the wargaming figures. They would be close to the immigrant Chinese look you're looking for.

You should mix in a few Europeans too... IIRC there was a substantial contingent of Irish workers, too, that were just considered a notch above the Chinese  at the time

Some cheaper gaming brands

https://www.ironcladminiatures.co.uk/ourshop/cat_970088-28mm-Boxer-Rebellion.html

https://victoriousminiatures.com/product-category/28mm-boxer-rebelion/28mm-boxer-rebellion-chinese/peasants-animals-houses-carts/