I have a shop made 14 inch, 2HP, 220V, 3450 RPM, 1-1/8 inch arbor grinder (photo att) that came out of an old commercial blacksmith shop.  It looks like it may have been modeled on a similar size grinder sold by Champion in the 1920s.  It came with only 2 wheel flanges (a wire wheel was mounted on the other side with washers for flanges), so I need two more flanges.  I don't know all I need to about grinder flanges though.  The flanges that came with the grinder are so thick and heavy that grinding wheel width, especially in larger diameter wheels becomes an issue (not enough arbor length).  How important for safety is mass of the flanges to the size of the wheel, ie. can I use lighter, thinner flanges to allow wider wheels?  How significant is the ratio of flange diameter to wheel size, (smaller diameter flanges are available that I would have to drill out a larger arbor hole)?   If anybody knows of a web source that talks about this stuff, I haven't found it yet, and would appreciate a point that way.  I have a feeling somebody here may already know the answers. Thanks.

Buffing flanges are close enough.
Mcmaster has them of course.
Nobody is going to have an off size though. I'd get 1" and bore out to 1 1/8.
$30 a pair for 4 inch diameter.
http://www.mcmaster.com/#buffing-wheel-flanges/=ik832u
or just paste 4899A44 into the search

Wonderful tool!! Big strong homemade grinder. Its just begging to make custom cutlery!! 
I tried to get a similar one once, but at the last minute Ted Beck wouldn't give it up.
Ted was a friend of mine and he didn't have many. When it came time for him to go to a rest home he had a big sale.
Total strangers could buy anything they wanted, but every single solitary thing I picked out?
He couldn't let go.
  Its happened to me many times, same thing.  Old friends just can't let friends have things that they care about.  I don't know why.

  I have been on the other side of it too.
  I was the stranger at the sale and could buy anything in sight, cheap, but the old friend of the seller standing there?  Nothing.
    People are weird.
   yours Scott

First off, let me say that is a fine looking grinder!

I don't think you will have much problem finding flanges to fit it, you just have to find an industrial supplier like MSC, or Grainger with the proper I.D. hole to fit the shaft and the proper O.D. to fit whatever stone you will be using. In any event, I don't think you should push the limits of the grinder by trying to use a thicker stone that interferes with the flanges/hold down nut properly holding the stone. That is a big shaft for a grinder, and I can't think of needing much more thickness in a grinding wheel than what it will do now.

Thanks for the information folks, it's been a big help.  I had never heard of buffing flanges.  I also found out that flange diameter should not be less than 1/3 the diameter of the wheel, so I guess a 4 inch flange will be O.K. for the 12"X2-1/2" wheel shown in the photo.  It's one I had laying around the shop, and looks about right on the grinder.  With thinner flanges there should be no problem about arbor length (the original flanges are 6+" dia.X 3/4" thick).  I thought I got a bargain when I got the grinder for $40 at auction, but it looks like it's going to cost about 5 times that much to get it up and going. 

have you a friend with a lathe that could turn up flanges for you ?

I don't know anybody that does metal lathe work as a hobby.  I know a couple of folks that run machine shops as a business, but I imagine their hourly rates make the commercial flanges the best buy.