You can definitely get RC buses from 80M model shop in Hong
Kong. You can order through their website: http://www.80mbusmodel.com/eshop/.
I've never tried to do so before, normally I will ask my friends
to buy for me when they go Hong Kong.
You can also try this Singapore website: http://bushere.blogspot.com/.
Not sure if he sell RC buses, but you can check.
Hope this info helps.