To begin with; top coverings come in various colors. Originally only black and white were factory offered.
OEM was also only in vinyl. Vinyl is still available for purists. The other than black or white are available in what I believe to be Hartz cloth. I have observed that white tops do not stay white for a long period and look dingy in a short period compared to other colors.
There are a number of Thunderbird suppliers. There is also some give and take between them in reproduction
parts. ie. One shop will make/commission a
part and the others will also sell it. No one shop is the overall supplier. I will probably omit some sources but that is only incidental and implies no like or dislike for them.
CASCO has been around a long time
Concours
Parts also handles
parts for other fords also. Owner of Concours originally started Larrys. He took some time off and could not resit jumping back in.
Larry's Thunderbird and Mustang
parts. also a long time supplier.
Prestige Thunderbird
parts also a long time supplier.
Thunderbird Headquarters also long time supplier.
Hill's previously bought out another supplier as they expanded.
National Parts Depot markets
parts for a variety of makes.
Mac's has Thunderbird
parts and is
part of Eckler's which is a longtime Corvette supplier.
I suggest comparing prices and shipping to determine the total cost on your doorstep. Again there are probably more but these are the ones that come to mind.
Some other places to my knowledge, like Jewell, only supply one type of specific Thunderbird
part. Jewell is a source for soft tops that are
OEM quality and have some interchangeable
parts with
OEM. There is at least one other top supplier that I know of, but I forget their name. I have seen their hardtops and they are okay but not
OEM quality nor exact style.