Hmm yes go the hks, the cheap dumps actually have cost a few people there engines as the wastegate hole in the dump pipe didnt line up with the wastegate and hence in turn the wastegate couldnt open all the way, causing higher boost levels then anticipated.
Its gonna be hard to get the hks dumps at a good price from japan as the dollar is down the creek atm , so local in stock will be your best option,
try japanese import spares they are in SA thought they might have some 2nd hand ones or new ones, i can check them out if you require
http://www.japaneseimportspares.com.au/home/