Brenda, nobody knows what they don't know, I only know what I know . They're just ordinary HSS drill bits. The smallest drill bit I use is 1mm, it allows all my blades up to No. 5 to go through. Sometimes if there is space I will use a larger bit just to make threading the blade easier.
One thing to remember about small bits is having a chuck that will hold them, I had to take the chuck off of a hand drill to put in the pillar and cordless drill to hold the 1mm bit. You will need a chuck that closes to zero.
If you have a Boyes shop close by they do 1mm bits in packs of 10, also available from mail order suppliers like from here, https://www.ukdrills.com/hss-drills/hss-metric-drill-bits and most drill bit suppliers. Screwfix, Wickes, B&Q and the like will have them but will be dearer. Also if you do markets and car boots look out for them there.