My 2c :
What you need is not an overly short bbl, but rather a shorter stock.
I just paid a trip to the local store and tried on some Stoeger over/under in 410 (chromed) and some blued sxs, in 410 and 20ga.
They have short stocks and I wouldn't mind shooting them, but I was looking with my son and wife in mind. Both really short.
I have a backpacker and the length is 12". A no-no in US.
I got 5 grous in one session last year.
a 3" .410 #6 has 97 pellets. A 2 3/4" 12ga. #6 has 192.
Is it really that big of a difference?
I got a 7 year old that likes shooting it, but the short bbl makes for a big noise,,,,, If I was to buy one I'd get the sxs or o/u with a smaller stock. They were about 4-500$.
If you're good with wood, you can go on a budget, get the backpaker and shorten it a little bit.
One bad thing about the 410 though : no chokes. ever.