1"-14 is a pretty common die size for the really big cartridges. You can get them from RCBS/Huntington, CH4D, Redding, and probably a few of the other makers still offer that body size dies & blanks.
I haven't seen any 1.25" dies before.
That's the thread size that the RCBS Rock Chucker and a few other presses are threaded for if you pull out the bushing. The Rock Chucker comes standard with 7/8" but they also offer bushings for 1" dies.
The RCBS price code for their 1" dies is "X"...any X group dies are 1" body and they're a special order item. And just like CH4D's big dies, the pricetags will scare the pants off ya!
As for any C-H distributors. I'm not sure if they market anyplace besides direct marketing. Kevin is probably right in that you go straight to them.
I went directly to them when I needed parts for my old 333. They were nice friendly folks to work with too!
If you do get one of those Champion single-stage presses, I can just about guarantee that you will never wear it out or spring it out of shape...but you might get a hernia hoisting it up onto your bench!
They are built hellferstout!
Unless you're looking at doing some serious case forming I doubt you'd need a press that strong.