You could always build a SxS on a .410 frame!
Either the CZ or the mini-mauser in 7.62x39 will work fairly easily. The bolt face is close enough to go w/o alterations and you have plenty of magazine length for rifle bullets if you want. Feeding is the biggest issue. You can use a slightly modified 223 follower in the m-m. I haven't tried the CZ, so???????
