since you spoke with PUI directly, I'll take that estimated date. Summit's website says est. drop ship November 14th...
https://www.summitracing.com/parts/pui-85gnusc05u/make/buick/model/regal/year/1987
HighwayStars website shows them in stock. Item listings states to call them if you don't need the full set which probably includes the rear seat and front headrests. they will sell pieces from the full set, per the listing description below.
Interior - 1985-1987 Grand National Seat covers - Complete Set made w/EXCLUSIVE MATERIAL w GM LICENSED TURBO 6 Headrests (included in this set)
opgi (original parts group) sells PUI stuff....probably out of stock....I did not fully research this.
thepartsPlaceInc has seat covers in stock (per their website). most likely made using the reproduction pallex material which is slightly different from original pallex to the eagle eyed individual when compared side by side.
scroll down about 3/4 page on link below...
The Parts Place
on HighwayStars product page, there is a pic with the different materials side-by-side. the pic can be enlarged for better detail and comparison.
there was a really good thread comparing the offerings of seat covers from many actual manufacturers and who sells them. it was from late 2020 and is part of the batch of threads from May 2020 thru March 2022 that admin is supposed to re-integrate and restore to the forum.
but that doesn't do you any good at the moment. in that missing thread was a youtube video of the PUI set being installed and a review of the material. with HS noting their fabric is GM approved as part of the GM Restoration Parts Program and is exclusive to them and it's in stock, I would look at contacting them in the morning to learn the details and availability for what you need. then compare to parts place's offering.
yes, it seems like the world is upside down for two years and counting now. I had to search high and low to find 3/8 and 1/2 fuel hose for the filtration system on the parts washer. seems nothing is in stock anywhere anymore or it's priced like gold bars.