Perhaps with detailed photos and specs one of the skilled forum members in 3D printing would gladly assist you in adding a much-desired detail to your outstanding model. I'll bet a new thread from you asking for help would do the trick.
Door handles appear to be what you are missing. Out of all the O or "quarter scale" detailing products that are available, door handles or levers are a real rarity. You can find many of them in 1/12 and even 1/24 scale, but not 1/48.
However, I know the source for these although they might be a little "domestic" for your purposes:
These are old fashioned white metal accessories, which are bigger, rougher but also more durable than 3D printed stuff. These are listed as 1/8" long or 6 scale inches. I have never found 3D printed handles in O scale although I have looked.
The source is http://www.virtualdollhouse.net/VDSTORE/Metal1.htm. I have got many items from the lady who runs it, who is called Grace.