Do you have the hub caps? Just curious. Because the original wheels take an obsolete hub cap which fits inside the raised inner ring.
They can be bought but they ain't cheap.
If you buy new wheels you can buy standard style hub caps which look too big.
Maybe you could try wheel covers or chrome lug nuts with trim rings.
Or maybe even mags from a seventies car.
They still make trim rings and also hub caps which attach to the lug nuts...you would have to check for fit on your wheel and of course get four lug ones.
If you choose wheel covers you can use them even after you change wheels and axle
some day if you ever do, also wheel covers can be used on regular trailer wheels if desired.
Here is an example of rings and caps on a trailer wheel...
you could also paint
the wheels for an accent color.