There used to be a highly detailed B25 for Microsoft Flight Simulator. It looks like it has been updated for FSX (Microsoft Flight Simulator 10).
http://www.maam.org/php/xcart/MAAM-S...9-p-16134.html
You should be able to pick up FSX quite cheaply, it is about 18 dollars at Amazon, but you might be able to find it more cheaply somewhere else.
There seem to be free add-on textures here,. but some are for the older version of the download:
http://www.maam.org/flightsim/enhance/b25_enhance.htm
It might not quite be up to the standards you require. I assume you are really looking for something better than the Forgotten Battles/1946 model, and I am not sure that this one is.
It looks like it's a paid download - 30 dollars - maybe the older versions (FS2002, FS 2004) are cheaper, or free.
There's a multi-media CD and some free stuff here:
http://www.maam.org/airshow/b25.htm
.