I know that from the BeerSmith website you can download ingredient packs. If they are in the same sort of format you might be able to use those. Worth a try. They are .bsm files, so I hope that ProMash supports them.
Look at the Grain Extensions that can be found on this page. http://beersmith.com/beersmith-1-4-support/
I have no experience with ProMash, but it may have an option in it for addons to download more ingredient files.