My oil dipstick tube broke right where it goes into the pan. What is the remedy? Where can I get a new one if I need to?

you could thread a tap in (grease it to catch chips & dont go all the way "thru"). to avoid the chips a person might grind a right angle leg at the end of a bolt & go in & hook it on the end of the broken dipstick & slide hammer it back out. EDIT If you tap it you might first pack some grease down to the very end of the broken piece as a barrier to keep shavings from falling down into the pan

As scary as it may sound you can get a long skinny screwdriver and push the broken part into the pan. I'll fall to the bottom and be waiting for the day you pull the pan. Zero chance of it getting lifted into the spinning bits unless you flip the engine upside down.

What Mopar V8 has the dipstick going into the oil pan except the class A motorhomes and large trucks? If it is broken off in the block I use a 318 pushrod from the bottom with the oil pan off, to drive the old piece out I have tried to use a flat nose punch to drive that piece out and ended up buggering the block up

A traditional easy out will remove the broken end out of the block, and yes a new one can be installed with the engine in.
Jack it up, sand / grind a small chamfer the end of the new tube to get it started, seems like I used some lube as well.
Takes two guys to install, one under to guide it and another one to tap it lightly into place.
I typically use a short screwdriver in the end and tap on the screwdriver.
NO CHROME TUBES... they are too big around to fit easily..., buy a resto type.