I have just checked on MLU Forum and the last time "Simex" was written in a post was 2007, so I think you may be reading old posts on there. I did buy some Trackgrip tyres from their European HQ about 6 years ago, since then, the company has come under the German tyre maker, Continental, which has caused the problems I understand., and sadly this source has now dried up, never saw any 12.00-20 anyway, it was 9.00-16 Trackgrips they brought in ( not Runflat).
As for approaching Simex USA, I think it would have been better to have gone straight to Malaysia, as the USA base, would only have been an importer, not manufacturer, so no different than talking to the European HQ.