Are you looking for the endemic plants Rubus hawaiiensis, and R. macraei. Or thimble berries, or other naturalized types? Unfortunately I dont have access to any of these, unless I go on a hike some time soon, and try to collect thimble berry seeds.

Mahalo, Aloha,
Matt garma

Here is a link that might be useful: 'akala berries

If you are using them for research, your seed source should probably be a reputable institution that accessions and records the collection, just to confirm species identification. Try contacting the National Tropical Botanical Garden on Kauai or Department of Agriculture, State of Hawaii.

... and please don't let them escape ... birds can spread the seeds and they grow to form impenetrable thickets, can really get to be a problem, as they have on Kauai and Maui.