Another user gave me this to answer my question:

How to use Commerce Feeds to Import Stock for the Commerce Stock module?

The user http://drupal.stackexchange.com/users/8943/watergate suggested this:

1. If you're using commerce_feeds 7.x-1.3, uninstall it.
2. Make sure you've updated the standard Drupal feeds to 7.x-2.0-beta1
3. Download commerce_feeds 7.x-1.x-dev

After I did that, I could use mapping and see all the target fields for my product variation, including those fields enabled when you use commerce_stock.

Another user gave me this to answer my question:

How to use Commerce Feeds to Import Stock for the Commerce Stock module?

The user https://drupal.stackexchange.com/users/8943/watergate suggested this:

1. If you're using commerce_feeds 7.x-1.3, uninstall it.
2. Make sure you've updated the standard Drupal feeds to 7.x-2.0-beta1
3. Download commerce_feeds 7.x-1.x-dev

After I did that, I could use mapping and see all the target fields for my product variation, including those fields enabled when you use commerce_stock.