My seat cover has been changed and has the cloth inserts for the driver and passenger with the vinyl in the middle so I don't really have anything to show an upholstery shop unless I could get a picture of one somewhere.
You're not talking about this color/pattern are you?
That is a common 1979 seat cover style - but it's for the Custom Deluxe trim level. I doubt it was offered at the Silverado level.
But, if it is what you are looking for - bump this. I might know of a source for OEM material.
Check your RPO sticker.
The RPO is 25V and the description is, "VDD1 Blue Vinyl Bench".