That was strange as I went to our local Seal supplier who are 20km (12 miles) away from where I live and they will sell you however many you want.
I discovered afterwards that a bearing supplier 5km (3Miles) from me would have got them for me also in packs of 5, 10 or 20.
The fellow in the bearing suppliers was really helpful and informative and gave me this information
Viton®, Dai-El and Technoflon are brand names for FPM polymers also called FKM. All of the designations stand for one single base material, which is fluoro rubber.
This has two standards associated with it
FPM is the ISO designation and FKM is the ASTM designation. ISO is the International Organization for Standardization
ASTM is the American Society for Testing and Materials
They have a term called shore hardness associated with the seal and medium Hardness is 80 which is best for use in the carbs.