About the best I have been able to come with so far is this:
https://www.utrechtart.com/Utrecht-C...015785.utrecht
The divider measures 21.5 high by 48 wide, but the 48 includes a 2 inch wide pointed edge for about 2 inches high that honestly you can't see anyway from the trunk. You could get the thickness by getting the 1/32 and 1/16 thicknesses and gluing them together. This is all I have been able to find in single sheet sales that is reasonably priced.
Hope this helps.
EDIT: I went ahead and ordered a sheet of the 1/32 and the 1/16 and I'll let you know what they look like. 15.00 bucks what do I have to lose?