Typically some 1N4001…1N4007 in SOD-123 or SOD-123FL package is the cheapest available diode. It is available from many manufacturers and at all distributors.
The typical rating is:
- 1A forward current
- 1000V reverse voltage
- Instantaneous forward voltage of <=1V @1A
On LCSC, a full reel (3000pcs) of SOD4007-MS by MSKSemi costs just 6,60€