I mostly find lady slipper orchids during orchid shows. I am not familiar with Fresno, but if I search online, the one that shows up where orchids are for sale: not sure though if they carry slipper orchids, but you can try and see
1) Orchid Barn
2) The Elegant Orchid
If there is none there and you are willing to do a bit of a drive, go to Sta.Barbara where Sta. Barbara Orchid Estates is, or call them first if they do have slipper orchids, to save you time and effort.
Good Luck! Hope you can find one, or if you can attend Orchid Shows, there are always vendors there that carry slipper orchids grown from nurseries. I attend if I can Pacific Orchid Show in San Francisco, this year it is in Feb 21-24, 2019. I make the effort to go there if I can, that is where I really see good specimens.