I too use my old Trac II razor from back in the 80s maybe. a ‘blade’ lasts me a month.
You're as cheap as I am. I use the Trac II and found blades on Amazon at $6.69 for 50. I note they're now up to about $9 and 100 blades will run you $14 or so.
It's not the original Gillette blade but a name brand:
Personna - Twin Pivot Plus (50 Blades/Order)