Kiddie bike trailer wheels needed

[Sarah]

I have been given a kids trailer to take my elderly Border Collie out in

Problem is, it only has 1 wheel

I would like to get a pair of wheels preferably. Current one is 16" and has a 4" axle held on with cotter pin. If I could get a pair of these would be great. Also considered running an axle thru and putting an old set of 26 my bike wheels on it.

Any suggestions, ideas, offers etc please?

Thanks

Sarah and Pluto, the old bc.

[Bearbonesnorm]

What diameter is the axle Sarah? I'm assuming 4" is the length?