CD26/ DPP4 expression in skin fibroblasts is involved in the fibrosis in the process of wound healing. PDGFR-alpha is also a famous marker to identify fibroblasts and is not expressed in epithelial and endothelial cells.
Ref
Science 17 April 2015:
Vol. 348 no. 6232
DOI: 10.1126/science.aaa2151
RESEARCH ARTICLE
Identification and isolation of a dermal lineage with intrinsic fibrogenic potential
You could also try differential trypsinization and re-attachment - fibroblasts usually attach faster to plastic than epithelail cells, so you could let your trypsinized cells sit for 15-20 min to adhere and then collect the unadhered cells as the epithelial fraction - do this a couple of times and you should get rid of fibroblast contamination. Check this by expression of eg. vimentin - there should be no vimentin positive cells left.