I just replaced the photo-eye in a Whitfield Profile as it would light then switch off after 15 -45 minutes even with a burning fire. After I removed the old unit I noticed that it was a Honeywell Plug & Play replaceable CDS unit so I sourced the cells and found they cost $11.95 each. They are standard Oil Burner cells any HVAC company would stock. I now have 2 spares on the way. Thought it might be something you could pass on/use with customers. I paid $60 + $15.5 for the new complete unit from a place online. A guy on ebay wanted $169 for the same unit!!!
I'll be refitting the old housing with a new CDS cell next time.
Part # Honeywell 130367