Before you buy your seat from one of the US/Canadian cycle part suppliers please find out who actually manufactured the seat.  There are different levels of quality, some are downright awful.  To avoid being disappointed you may need to ask some questions.

Personally I have been very happy with RK Leightons seats. And I was very happy to get a tour of RK Leightons 2 weeks ago when I was in UK.  Andrew Leighton is very knowledgable on his subject matter and a nice guy to meet.

In RK Leightons well organized but surprisingly petite workshop you are greeted by rolls of vinyl, the whirr of stitching machines and the occassional whiff of contact adhesive.  Freshly completed seats and one-off specials sit on workbenches.  A mass of carefully labelled hardboard patterns templates used to cut the correct sized parts for almost any of the hundreds of variants of seats you can think of hang on one wall.  Seat vinyl is carefully selected for grain/weight and closeness to the original material used by factory. A pile of original seat covers, un-picked, sat in one corner.  I presumed that these were new additions to their catalog of seats and had been,or were to be, used as 'masters'.

Seats requiring special 'silver/gold' embossed logo on the rear are done on the premises with special dies - no AMC seats require this, but m/c logo is on many of the late BSA, Norton and Triumph seats.  Seat pans are manufactured locally by the same OEM supplier that contracts for Jaguar (I think).   Covers can be stitched with or without piping.

Even the seat foam is custom-formed for RK Leighton closely to original specs so to get the original, and correct, seat contours.  Without this attention to detail some aftermarket seats can look like a 'slab'.   Be warned :-)

If you ever happen to be in Birmingham UK (Birmingham does have an excellent International Airport) and have any need for covers, seat foam or complete seats I'd recommend calling or emailing Andrew to pick up in person if you want to avoid postage costs.  Jim Reid has kindly provided the contact info below.

Hope that this helps anyone who is considering a new seat.
Rick Mann
(usual disclaimers - I have no commercial interest etc., etc., but in true disclosure I should add that out of all the places I visited while I was back home RK Leightons provided the best cup of tea .... and I was 'pleased as punch' to be able to buy a 'correct' light beige seat cover with blue piping for my 18TCS.)

Over the pond....