Can't find it. Looked & looked - Fuel filler door pop rivet
The parts catalog -SHOULD- be able to help, maybe I'm blind. (pg. 20 of parts catalog, filler door is item #:4 -illustration shows -popper- & -bumper- no rivet)
Tried to add a link to parts catalog .pdf , but, no joy

Seem to have come close with this:
https://www.gmpartsdirect.com/oem-pa...rivet-11611736
, but the fitment list doesn't include HHR
Priced like gold, and by all indication the proper rivet is special. Like to get it right if actually needed.

 

R.A. lists it
https://www.rockauto.com/en/parts/gm...,rivet,1001742

Looks like a standard 3/16 pop rivet

 

I'd end up using aluminum pop rivets, because popping the stainless ones hurt my hands.

 

That one on their site is all well & good (even with the GM platinum pricing !) , but, I don't know if it's the right one.
And it doesn't look like any standard pop-rivet I've got in -MY- arsenal.
I just found that number willy-nilly on the inter-webs, and the fitment chart didn't include HHR .
.(-R.A., of coarse, insists on using an exclusive shipping warehouse, so include -another- $10 shipping charge. (Pirates) )

 

Beside material, what could possibly be different between pop rivets? Measure the diameter of the hole and the length needed. Or, put simply use one that fits. Not rocket science!
Do you expect something horrible to happen if you use the wrong brand? What would that be? GM does not send inspectors around looking for things.
You must have waaaay too much time to be worrying about that junk. The reason they don't specify is they don't care, they use the ones that fit.

 

Some factory rivets are a touch smaller size , some larger. Machine screws and nuts will work also

 

Pop rivets come in 1/32” diameter increments, from 1/8 to 1/4. Various lengths. I think maybe 1/8 and 3/6 are the most common hardware store sizes.

 

Used to be two? Aluminum and steel various sizes...

Now the inner fender panels and trim parts are held on with "poly" rivets.
Can't use the old tools Harbor Freight does sell a kit for $17 tool and rivets
Original equipment from the Dodge dealer $8 each. 2001 Magnum wagon
Anything else but a pop rivet will come out. Except a zip tie but doesn't look good.