Pneumatic jockey wheels

Hi all

I have been looking at replacing my very worn solid jockey wheel with a pneumatic one.  The only problem is that there is limited clearance under the A frame due to motor mover equipment and ideally a 200mm diameter wheel is needed in order to give adequate ground clearance when retracted.

Does anyone know where I can get a wheel assembly of this diameter as I can only find the 260mm version of which there are many?