The owners handbook lists the space saver sizes... and 13" is too small for any post-2012 Panda:
For all model 312 Pandas with 165/70 R14 or 175/65 R14 (14" rims) or 185/55 R15 tyres (on 15" rims) , the space saver is the same for each = 135/80 R14 (note it is important that both the space saver wheel and its tyre are the right size).
For the 4x4 models with 175/65 R15 15" wheels, and Cross 4x4's with 185/65 R15 wheels, the spacesaver should be 125/80 R15 (note the 4x4s need the bigger 15" spare to clear the larger front disc brakes on these cars)
Using a 14" spare on the 4x4/Cross can cause damage to the 4x4 system too.