I have bought a 2001 f4i track bike which has come with two sets of wheels, wet & dry. However the two front wheels are different widths. The one which fits properly has an internal width width of 14 cm, the other 13mm. Hence it won't fit properly and is sliding side to side. They are obviously from two different models.My question is where to get spacers that will sort this out.

 

I'd start with a hardware store. I've been pleasantly surprised by the variety of things like that I've been able to find at a some of them!