I do the same here in the states, but I hadn't heard of Somi until you mentioned it just now. The only China import I'm aware of is UBlast, which has been received with mixed emotions among my fellow tradesmen.
It appears Somi is PVC (not rubber). PVC works very well so long as you use fairly worn abrasive. Sharp, new abrasive tends to destroy it easily.
Somi only seems to be available through Alibaba. Just be careful who you deal with.
JB