Where can I purchase?

Not sure where you're located, Jim. Here in the Vancouver / Victoria area in Western Canada there are a few places that take over failed restaurants, bakeries, etc. and sell the equipment and small wares, sometimes at auction. Here is an example that comes up when I do a Google search on "restaurant auctions Vancouver" > http://kwikauctions.ca/. You could check your area for a company that does that.

Use this helpful chart as a guideline for the most common loaf pan sizes & volume:

5 3/4" x 3 1/4" x 2" (mini) = 2 cups

7 3/8" x 3 5/8" x 2" = 3 cups

8" x 4" x 2 1/2" = 4 cups

8 1/2" x 4 1/2" x 2 1/2" = 6 cups

Maybe something like this?  Other than not having handles, it sounds like what you are looking for.

One suggestion offered a few years back to the same question was to put two pieces of dough in a regular pan.  The baked bread easily splits into two demi-loaves.

Paul

9 1/4" x 5 1/4" x 2 1/2" = 8 cups

Hubert is a restaurant supply place in Canada. They have what they call 'demi loaf pans' (that seems to be the accepted name for these) for purchase. https://www.hubert.ca/product/28731/Chicago-Metallic-Individual-Demi-Loaf-Aluminized-Steel-Bread-Pan-38-lb