I missed the Siaga bandwagon allso. The Kel Tec KSG tactical shotgun looks promising. It's a 14+ 1 pump bullpup. Twin 7 round magazines with a lever to switch between tubes. However it won't exactly be inexpensive at first either.
The MSRP is going to be right in the ballpark of 880$, Kel-tecs hardly ever go for a lot (the Forward ejecting bullpup notwithstanding.)
The hard part is going to be finding one that hasn't already be paid for. There is at least a 6 month waiting list after they begin production, last I checked with my local gun store.