This response is based on the information provided.  We suggest you discuss with your contracting team, program manager and/or legal department as appropriate. 

It appears there are eight small businesses with CHESS contracts.  You can contact all through an RFI or a memo/e-mail to all small businesses with CHESS contracts.  The document should have an accurate synopsis of what your unit is acquiring and the timeframe.

We believe you already have justification to presume a set-aside - eight contractors have contracts.  Unless there is something particularly unique in this requirement, all are likely able to provide.