I've heard of Megazip but AFAIK that website is located in Ru ssia, so now might not be a good time (or ever) to deal with a website in that country.
WHOIS search results from Go Daddy, I disabled the links to .ru web sites so they don't work by clicking, don't want to send anybody to a ru...
After reading your post I went back and saw there are two different 1603 sections, I went to the other one and stopped looking, then went back and found the studs that face out for the Tstat pipe. The upper studs appear discontinued, so looks like the quickest option is to buy the Tstat housing...
The studs I was most looking for (90029-01506) are the smaller studs that point upward from the Tstat housing, those appear to be discontinued in the US, maybe available from Japan (Amayama lists them, Partsouq does not). I would guess that there's a substitute out there for another vehicle...
Was looking for a source (part numbers) of the studs that are attached to the Tstat housing of a 1FZFE (see diagram which says see Fig 16-03). It appears that the only way to get those studs is to buy the housing??
There are two studs that point upward and three studs that point horizontally...