Have you tried Peter Tan in Hong Kong? He runs Suneast (which used to be Tan14 - still uses that web address).
Peter can make up stainless steel custom weights up to 2kg.
I've bought from Peter a couple of times with no issues.
Scroll about two-thirds down the linked page:
http://www.tan14.com.hk/suneast/24-O...ccessories.htm