Aftermarket, none that I am aware of. Has been a lot of talk about remanufacturing but cost Vs. volume had knocked it on the head.
I've got an RM400 (shares the same rod) and I’ve been looking for many years & found nothing. Was lucky enough to find and fit a NOS pin, bearing & thrust washers that has bought me some time. I’m sure that there will be someone that has one and will pop up there head one day.
To save you some time I have trawled though all the web sites and catalogues (eg BBI) etc. & can’t find anything close enough. I did find one but it was 4mm longer and would have meant the fabrication of a 4mm spacer to go under the barrel which would have stuffed up all the crank volumes, exhaust pipe locations and the carby to air box connection, in short not worth bothering.
They come up in the states from time to time but the demand in the USA means that no one is interested in going through the brain damage to deal with us and pack/send to Australia when the have local guys jumping over each other to get hold of one.