Slavia 618

Knibbs and Chambers do not have them and Waffencenter Center either
you are in Canada and the screws would be Metric so you will have to source them online or Ebay
from some quick reading they are m5 x 30mm but more Google search could be advised
and they are special screws with small heads
i would send these guys a message
https://dlairgun.com/collections/slavia
while i am at it
https://www.pyramydair.com/blog/2020/07/slavia-618-breakbarrel-air-rifle-part-3/

about all i have good luck i would try a hex button head screw and then resize the head as needed