door sheave for port a port hangar

I'm wondering if anyone has found an alternate source for door sheaves. Port a port parts carries them for $50 + $10 shipping. I need 2 of them. They are 4 3/8" x 7/8" and I think the bore is 5/8", but not entirely sure on that one.

One of mine is locked up and I can't get my main door open without considerable effort. Looks like lubrication will be a yearly maintenance item. Unfortunately I can't take the old one down until I put the door up since the springs are under tension. Once the door is up it appears that I can pull off the sheave to replace it or oil it. Mine need replacing anyway, looks like they are pretty grooved on both sides.

Jeff

Sheaves

I tried to find alternative sheaves many years ago and found some at a local bearing supply (Kaman Bearing in So Cal). They were fine dimensionally but failed in short order. Long story short, I bought the port-o-port sheaves and never looked back.
Inspect your cables very carefully for fraying that may have occurred from your damaged sheave. A broken cable can ruin your whole day.

Thanks for the pirep Steve,
I broke down and ordered a pair today. Can't believe that I can't find a comparable product.