Had time for measuring. A Belinda ammocan (840 rd 5.56) exterior measurements seem about the same as your .50 cal can (if you measured exterior). About 5½ wide/side to side. About 11" long/front to back. About 7" deep/high. So maybe the box from a Belinda ammocan would drop right in your .50 cal can. IIRC, the Belinda ammocan held about 100 6.25x45 cigars standing upright on their feet. Again, not the best cedar, but a decent cedar plywood box.
Some good cedar boxes would fit in, with room left over. JR Ult No. 1 (holds 25 cigars 7.25x54) is about 7¾ wide, 4 and 5/8 long, 4¾ deep. JR Ult Presidente (holds 25 cigars 8.50x52) is 9 and 1/8 wide, 4 and 5/8 long, 4 and 5/8 deep.
Some combinations would get two good cedar boxes in there, with room left over. Could put a ERdM robusto suprema (holds 20 cigars 7.25x54) slide top box, and an Excalibur I (7.25x54) ten cigar box in. Or put in an Excalibur I twenty cigar box and an Excalibur I ten cigar box. Lots of good cedar, less room for cigars.
I've got some thin cedar sheets from cigar boxes that would fit. Would get cedar in the ammobox without taking a lot of room. Would not look as nice as the Belinda box or cigar boxes, but lots of room for cigars.
If you want any of this stuff, I'd be happy to mail it to you. Not looking for anything back my way.