18 inch Trailer rims Blitz Semi Pontoon Trailer

[Brett Nicholls]

Hi,
I'm on the hunt for 5 Trailer rims 6 stud 18 inch which I think are going to be hard to get and the same with suitable tyres.. These are for a Blitz semi Pontoon type trailer. So my current idea or alternative is to graft the centers of the original rims(which are way beyond useability) into Blitz 20 inch rims and down size the tyre to say a 9.00x20 so as to have roughly the same overal size as the original 10.5x18 and not have the problem of finding 10.5x18 tyres. Does any body have any suggestions or a suitable alternative? Thanks.
Regards,
Brett.