Is there 28 hole front/rear drum brake hub
I've seen 36 and 48 hole brakes, but not 28. 28 strikes me as an unlikely number because hub gears/brakes are not usually made for especially lightweight bikes. Harris Cyclery only have 32 hole and 36 hole in their parts list, and I can't really make enough sense of the Shimano web site to really be clear on the options. Note that Shimano make "roller brakes" rather than drums, and those clip onto the side of the hub. Sturmey Archer drums all seem to be 36H.

If you are willing to really work at building the wheel you could cross-lace a 36H hub into a 28H rim, but you wouldn't get an especially strong wheel and it would take a lot of work (I expect you'd have to do it experimentally and that really means having a range of spokes sizes available on a "pay for what you use" basis).