I got a months supply shipped via vPost for about $45. vPost is owned by the Singaporean post office... so I guess it feels a little less dodgy than other mail forwarding companies.
The service was pretty reasonable. They're meant to email you when the package arrives, but I found they didn't do that. I fished around their website for a little while and I found there was a way to look up your tracking number. Using that feature you can look up your shipment and register it in their system. So I recommend you check that site once a day after Soylent send you your delivery notification.
I haven't received my supplies yet. They are apparently still on their way to the vPost distribution centre. I'll report back on how the rest of my soylent journey goes.
BTW they send over air freight.