Hey mate, I contacted the good folk at http://www.bobthewelder.com (site closed at the moment, unfortunately) about a hobby pack of silicon bronze filler. They happily complied and made a new feature on their page where you could buy 5 rods or something for like 25 bucks. they may well have, or be ...

I went shopping for some Al Bronze filler and found some available locally in Brisbane, Australia but it only comes in a 5kg pack for $400! I reckon that about 0.5kg would be enough for me for a while. It is 2.5mm diameter. If I can find enough people who will buy the rest for my cost plus shipping ...