The only other place that I've heard of in Aus is referred to as the guy 'up north qld'. Every report I've heard is negative. So the only option is Electrosil or send it overseas. I'd be tempted to send it overseas as Electrosil have a monopoly and charge as much as they like and word on the street is they often underquote.

Langcourt in the US is good by most reports. $180US to replate ($20 extra if the have to remove the powervalve and another $20 if they have to remove the head studs). So remove them yourself if possible. Postage is about $60 - $70 each way. So potentially you're looking at $320 for a replate. Send a new piston over with it so they can match the sizes.

You're probably being pedantic about the cross hatching being almost worn through. If there is no scouring or chipping through in to the aluminium, quit your worrying!
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MC21 Honda NSR250. TYGA 300 conversion.