in addition to the R&D mAb noted above, you might also look at mAb B-A15 from https://www.antibodies-online.com/antibody/ and a rabbit pAb from https://www.lsbio.com/antibodies/ifn-beta-antibody-interferon-beta-antibody-aa39-66-flow-ihc-wb-western-ls-c165130/172477?trid=0