[galaxy-user] Bowtie index in data libraries

Hi, I have a galaxy instance where I would like to make some private data available to a specific group of users. The data I would like to make available are some bowtie indexes, so each index is made of several files with the same prefix. How can I do this? I have tried to put these files in a data library, but each file is seen individually, so it is not usable in the bowtie tool. I could add it to the bowtie_indices.loc file, but I see no way to restrict the access to a specific group of user. Any help would be welcome ! Thanks Anthony