Cache valley is a pretty rare arbo so not sure many institutes will have it. Your best bet is to contact CDC Fort Collins - they have a huge collection of arboviruses and are usually happy to share strains with research institutes that meet the necessary BioSafety criteria (I think Cache Valley is BSL-2 so shouldn't be many issues). The other option is to synthetically create the Cache Valley amplicon which is a great way of obtaining control material for rare viruses but has the drawback of requiring good molecular practices in order to avoid contamination!