Hi @hcole
Hopefully we can help!
I see the Homo Sapiens GRCh37 hg19 genome hosed in BWA-MEM at these two UseGalaxy servers. Are you working somewhere else? You could move your data over and work at these, too.
Am I misunderstanding something? Would you be able to explain a bit more? Thanks! 
XRef → Reference genomes at public Galaxy servers: GRCh38/hg38 example