402500 miles on my RAV4 - the idler pulley #2 center bolt that screws into the block.

I'm not completely sure which piece you are talking about but it sounds like you might be talking about part of the tensioner assembly. If this is the case then that piece will come with the new part.

How about a picture to tell us what you are refering to?

It appears to be the oil pump housing where this bolt screws in. The idler pulley #1 (the tensioner pulley) did come with a bracket but idler pulley #2 (more like a guide pulley) did not. We can't go with a larger bolt because it has to fit thru the center of the pulley then screws into the block or rather the oil pump housing. We're looking to try some JB Weld as a filler sorta like plumbers tape. What do ya think?

It is not going to work. The threaded hole for the tensioner is on the oil pump. You can make new threads for a heli-coil insert to make the threads original sized again.

This happened about 200000 miles back. At that time the original bolt broke off and we made a replacement bolt work along with JB Weld which has held all this time. Any idea where we can get another original replacement bolt?

I'd try the dealership first. They "should" be able to get you any part to your car. A bolt shouldn't be that expensive.