Check with Numrich Arms, also known as GPC (Gun Parts Corp) It's in their catalog and I think you can download the exploded view from them.
The model is obsolete, however we have a good supply of parts for that model. sales@countrygunsmith.net
Numrich gun parts
I would start my search at Numrich Gun Parts Corp.
Try Numrich Arms, they've got a website and a lot of used parts.
No
I would try either Numrich gun parts corp.or look at gunbroker.com.under gun parts.
You should be able to find a Exploded gun drawing of the Winchester model 190 at Numrich gun parts Corp.This will show you the position of the buffer plate in relation to the rest of the guns parts and positions. See http://www.gunpartscorp.com/catalog/Products.aspx?catid=7388
Winchester
Here is a site that has what you want, at least for he pre 1964 models: http://www.gunsworld.com/exploded/win94pre.htm
Exploded Firearms Books (soft cover) Editions 1 & 2 both have parts diagrams for this rifle and many other rifles,shotguns and pistols.
DON'T!!! unless you absolutely have to. you can cause damage if you don't know what you are doing. and parts are hard to find.
Try: Numrich gunpartscorp.com Jack First jackfirstgun.com Bob's Gun Shop gun-parts.com