That was Chevy's attempt to bring the customer back to the dealerships for replacement seat covers 1992 - 1994 , Until the cost of warranty repairs drove them back to sewn seat covers that didn't require a complete cover .I've done warranty upholstery/glass work for every major dealer Chevy/Dodge/Ford/Mercedes/Jaguar/Buick/Gmc/Pontiac/etc for more than 35 years
From what I remember they came as a 60/40 split and it looks like someone just mounted 2 drivers seats .
any good auto upholstery shop can custom build you a set of covers using those as a base but you have to understand they are foam injected covers meaning the seat foam is actually bonded to the material not sewn together and to reupholster them you have to cut off the material and formed foam to leave a flat surface and rebuild from there .. My DD 1995 GMC 3/4 Z-71 has the bonded type seats also
There is no reproduction original seat upholstery available as far as I know .Now I'm not talking about slip on covers I'm sure there are thousands of slip over covers available I'm talking about original factory type replacements.
Average cost to custom rebuild a set of these seats in vinyl material $900.00 to $1,400.00 depending on what style seats you want in the end .
When searching for replacements on any car use the word Upholstery not seat covers .or all you will find are slip on covers.