Is there any website i can look for them?

I was looking at BDK (http://www.bdkraceeng.co.uk/Bike1.html), they offer this ""Titanium Yamaha Kit Needles, 5CT-1, and Needle seats Y-O (we hone std ones to Y-O size) (As A Set) This is for CV carbs"".

Do you know if these needles and needles seats (i guess, they are the emulsion tubes) are replacemente for the 3tj?

Just buy a set of carbs off the bay

Actually i bought these carbs on ebay, the seller said that the bike was runing good.... I don't think so...

That's why i prefer to fix these and make them work properly, than buy another used set.

Do you know if those BDK will work?

If you follow the links and info in the BDK site you may notice the needles AND Emulsion tubes are advertised to be used in conjunction with open/bellmouth or Ram airbox CV carbs according to their setting page.

How much effect the needles will have on a std airbox fitted machine MAY be questionable.

I'm not sure about the carbs but what is actually holding you're engine in? !
Sorry I jumped 2 pages and 3 years when I read that just now
I see you have the right engine now!
Those bdk parts might cause you more problems getting them to run correctly on a standard bike.
Try calling Allen's Performance they do loads of Mikuni carb spares and might have what you need.

Thanks for the answer fellows;
I sent an email to BDK asking for the titanium needles working of a stock machine to see if they are reliable for a stock street bike.

And sent another to Allen's Performance to know if they have these needles and emulsion tubes in stock.

Regards, i'll keep you updated