Technical Help with an Idler(?) pulley

I am pretty sure this is called the idler pulley, if not school me....
And it's on my 1959 Dodge Coronet 326 engine.
But since these are impossible to find & pretty sure it's not an original piece considering the ****py job the mechanic did to my motor. I may need a plan B. Is there any other pulley off another car, a place to buy these?? Something... This is only thing left that's causing me issues.
It has to be a 3 V-Belt pulley. The bearings must be shot because it vibrates and making so much noise it sounds like a threw a rod. Frustrated and need my HAMB families help!!
MIKE
USAF, Retired

 

Hi
take it apart and remove the bearings. They will have numbers on them. Take to a bearing house and get new ones. install in reverse and it will be like new again.
Regards
Dave

 

Ones I've taken apart had a GM alternator number on the bearing.

 

Just what they said. It may be hard to get out , but the bearing guys I use have pressed a few for me