Surely you cut your own.
I don't think I have boght a gasket save the head one for nearly 20 years.
OTOH if you scan he faces in & send them to Steve at Britgasket he will happily cut you a set.
A client used to scan in the covers then use a vynal letter cutter to cut thegaskets out of whatever he put in there.
I used to think sheets of gasket papper were cheap compared to a finished gasket, but when you buy the stuff in 100meter rolls the cost is nearly nothing ( labour excluded )