hi Southtowns27,
i was curious if your drum was as difficult to find as some others i have been looking for,
so i did a few minutes of searching, and the answer is yes, the drum you seek is difficult to source.

5.809 drum assy., brake, front and rear
47-52 3/4 Ton front (exc. D-D) 3847128 (11 inch ID x 1-3/4 - 8 stud)

http://www.2040-parts.com/
claim to have 2x in stock used for $42 each, but description is not quite right, might be incorrect part

i suggest keeping a regular eye out on ebay and check junk yards
in theory i have two of these drums somewhere on my farm, but they have been removed from the truck years ago when the axle was repurposed for a home made trailer.
don't know where they are and what condition they would be in today.
if i find either of them in the next few months i will post again here.
good luck.
-s