Sounds unusual for the rails to be mangled, unless the car was in a
collision, so unless you inspected all of them, you may only have one
bad one.  Isn't it possible to straighten it out?   Otherwise the only
2 sources would be a salvage car or else MB.

As for the regulators, last Fall I recently bought one on Ebay for $75.
Same guy was later selling them for $50.   These are brand new
aftermarket ones.   They likely aren't as good as a new one from MB,
but the one I bought appeared identical to one that I'd bought online
from a regular parts store for $125.

If you get one of these from anywhere make sure to check the mounting
holes by putting the bolts in BEFORE putting it in the door.   On both
the one I bought several years ago and the recent one, one of the holes
was not tapped properly and I had to run a tap through it.   Pretty
good evidence they are made by the same outfit.

Also, be careful of the slide stop adjustment that limits how far down
it will go.  The aftermarket one used a regular bolt, while the OEM one
uses an allen screw type bolt.   I didn;'t notice this until I had the
whole thing assembled and went to adjust it.   The problem is with the
allen screw bolt you can adjust it.  With the hex head bolt, the
opening in the door frame is not large enough to get a socket in!   So,
make sure you check and if necessary, switch and use the old bolt.

And very important, make sure you lube up the gears with some grease
and follow the alignment procedure.   The window should work easily, go
straight, etc.  If it doesn't, that's what leads to premature failure.

Sounds like it's a dealer only item. Not unusual with
trim and weird body parts.

In real world terms this means "go findeth a parts
car". Try car-part.com and find the yard closest with
a chassis like yours.

Richard
the next 126 I buy will have manual windows i swear to god...