http://www.ubercart.org/forum/support/2626/q_how_allow_users_upload_busi...

This is a fairly standard practice it seems. There's another thread about this. Ryan I believe has come up with a portable solution that he's created a module for.

http://drupal.org/project/uc_node_checkout

Check out the thread for more information.

I know this response is a little late but I figured I'd direct future people in the right direction.

Cheers