Idler/Tensioner Pulley

So I purchased a 96 corolla from a friend, and upon buying it he told me the AC wasn't working. I have air blowing, just not cold. He also gave me a compressor, as his mechanic told him it needed to be changed. So when I get under my hood, I realize he was missing parts altogether.

I had to go purchase a new Idler Pulley along with the belts, and here lies my problem...

I don't have and can't find the lock bolt and nut that keeps the tensioner in place. I have checked a few local junkyards, nothing. Visited the toyota dealership, the guy working says he only sells it as one piece (pulley is sold with lock bolt). Wondering if anybody can help me find the part or give me the technical name? And if I fail to find it, would it be safe to go to Home Depot and get it cut myself? ( My brother has the same car, I could borrow his lock nut for the time being, but that's just to get an identical bolt if possible).

A bolt is a bolt and a nut is a nut. Just different grades or materials. I stripped the locking nut on my balljoint spindle so I went to the hardware store and got the exact replacement. Cheaper grade metal, but it does the job. Go for it I say.