I'm not 100% sure about the retail side, but I can tell you it's going to be hard to find. USDMYR is a restricted pair, because of Malaysia's capital controls - you can only really trade it through NDFs (non-deliverable forwards). Even when I was doing this on the institutional side I couldn't trade deliverable MYR.
Your best best would probably be "don't bother". Maybe try Saxo - they have a pretty decent range of currencies to blow yourself up in - or if you have a private-banking hookup, ask them; any decent NDF desk on the street should be able to quote you USDMYR NDFs.