Netbeans Manual Update

I have a Netbeans 8.1 development environment (linux) that is not able to be directly connected to the internet.  I'm trying to find and install plugin updates to download to a connected computer and then manually install those plugins.  

Currently I have downloaded the latest Catalog.xml.gz file, uncompressed it and added that file as a file://.../catalog.xml update site.  This allows me to see available plugins and updates.

I haven't yet found a way to locate the updated distribution Plugins on the Netbeans Plugin Portal, nor many of the dependent plugins that some of my previous plugins require.  

For example, I see
- Git version 1.19.3.1 is available as an update, but an unable to locate it in the plugin portal.

- The "FindBugs NetBeans Integration" and "findbugs" plugins require:
javax.jmi.reflect 1.5, org.apache.bcel 5.1, org.netbeans.api.mdr 1.2  ...  non of which I can locate in the plugin portal.

Thanks for any help you can provide.
Doug Brown