Try Buckeye Fasteners at 800-437-1689.
...or http://www.buckeyefasteners.com/doc/bfi-nut.htm

 

If your welding these "nuts" to sheet then maybe you don't need nuts at all..

What size thread are we looking for?

I could always drill and tap some round stock and send it to ya..
Then you can cut as many as you need easily with a saw..

Not a problem..

...zap!

 

The reason you don't see much in the way of weld nuts in aluminum is because aluminum nuts and threaded aluminum is notorius for allowing screws to come loose. I build aluminum ambulances and rescue units. We use the steel pressed nuts which actually work quite well. For some reason the exact brand we use escapes me but they're very similar to the ones at the bottom of the page microzone supplied. I'll get back to you when that comes back to me.

 

nutserts- thats it

 

Thanks to everyone for their help, with sources,and especially to ZAP, for his offer to make the aluminum part. But, what I was looking for was not to be found. We could not use a riv-nut type fastener, because we could not drill through the front of the sign face.SOOO, we went a different route. We cut up some 1"x1" square Aluminum tube, drilled a hole in it, inserted threaded rod, welded it down.



The item on the left is a steel "t" nut, (what I would have liked to find in aluminum)

 

tessdad - glad you finally found something you can use. I know what a search it can be to find the right piece or part. It is sometimes frustrating.