Nathan - My experience with having a foreign schedule done is that the QS who produces the report needs to be a reg tax agent here. They should obtain relevant info from their Malaysian counterpart.
The large firms tend to have colleagues in various countries and work co-operatively to achieve this. I have had them done in HK, Canada, USA this way.
Try BMT, Washington Brown, Depro for starters. The phone jockeys wont know about it. You need to speak to the MD ie Bradley Beer at BMT.