The British banger is not something one casually finds in the US, at least not in our experience.
Am not a Brit, but have been there thirty times or so and love pub grub. And bangers and mash is invariably on the pub menu.
There is no simple substitute for the banger to be found in the US.
We used to be able to find genuine bangers at a local supermarket, frozen, but that was when the chain was owned by Sainsbury's, a major British supermarket chain.
But no more.
You can find them on the web, but have never ordered from those folks.
Could make your own I suppose, we love making sausages. But it is a bit of a chore.
Short of that I would use a simple breakfast sausage for toad in the hole, but no mash there.
But I suppose you could make a mash of your choosing, put in some sausage, again of your choosing, and call it toad in the hole.
Of course toad in the hole is not that at all, it is sort of a Yorkshire pudding with sausages, but Scotland Yard, I am told, is not in the business of prosecuting those who call, well, almost anything, toad in the hole.
By the by, now when we are in London we rarely see bangers and mash anymore.
They call the dish sausages and mash, I suppose to be upscale. But bangers and mashed tatties is what you will get.
But you will no longer get beans with the dish. Many places used to serve bangers et al with beans (baked, more properly steamed, beans, the Heinz variety one finds in the cans), but sadly no more.
I suppose I shold have a point. I hate having to do that.
For breakfast take some breakfast sausages and make a toad in the hole - just Google for recipes. It requires a simple batter and is quite tasty.
For lunch or dinner, take whatever sausages you like and add serve them with a mash. It will be good.
And they should be served with a bit of gravy. But that is another matter.
Canned or jarred, perhaps with some caramelized onions will work just fine.
Just my take on things.
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My mom used to tell me don't criticize anyone until you have wallkd a mile in their shoes - at that time you will be a mile away and have their shoes. Mom's always know best.