Brick and mortar store where I can find pressure relief valve?

[CSBudzi]

My regulator pressure relief valve is leaking quite a bit. Regardless of pressure (3-5 psi even). The local brew shop is out of the part.
All the friends are coming over for the start of the hockey season tomorrow (go hawks!). No time to shop online. Plus I always try to buy local.
I tried scouring the forums for a real store I can go to, to get the relieve valve. But I couldn't find any help. it looks like home depot, Menard's, etc only have 150psi and above relief valves for air compressors.
Please tell me if I'm wrong but the regulator should have a relief valve around the 50-60 psi area.
I'm in the far west suburbs of Chicago. Anyone have any ideas where I can find an appropriate psi regulator relief valve?
(Note I did try reseating the valve)
Thank you for any help. And I'm sorry if I missed something obvious, or a previous forum post.
C. S. Budzi

 

[The10mmKid]

There are three GRAINGERS near your ZIP

Maybe a restaurant service company would have some CO2 stuff.

'da Kid

 

[Onkel_Udo]

Welding supply and hydroponics are the only two not listed so far. If nothing else, wleding gas supplier will have a regulator.