Leads for pencils for pens are quite different than leads for Victorian pencils. Earliest pencil leads standardised at 1.18mm and there are plenty of supplies of old leads. 1.05 mm leads have been a problem but there are solutions using a 1mm lead to give good results.
0 .9mm leads are the normal later Parker and Sheaffer fineline leads although some Parker leads were 0.7mm

Our stock includes all the ranges except the 0.8mm leads.
We suggest that you try softer leads such as B, 2B abd even 4B for writing
Prices for 10 leads are

1.00mm

 
1.05mm

 

 

1.15-1.18mm  
1.50mm  
1.80mm    

2.0mm

   
Other sizes on request