1 - the dynamic brake blister from a MTH, Lionel or Williams GP-9 should do the trick.
I'm not saying that you won't have to do some modeling or modifying to make it fit, but scale models of the same prototype should be consistently about the same. In my diesel
experience, MTH tends to glue these blisters on with Atomic Glue (I took the blisters
off my GM&O GP-38's...it was an adventure), but Williams and maybe Lionel take a more
casual, pop-on/off approach.
See eBay for a dynamic-brake-equipped body shell or even just the blister.
2 - I just gathered 3 MTH locomotives for a comparison: SD45, SD9, SD24, and
looked at them one on one on one. (BTW, the SD45 photos that I have - Southern
Railway - show the locos with the modern HT-C truck, not the older double-clasp type. This HT-C matches my MTH SOU SD45.)
- the MTH SD9 - it has double-clasp - truck side frames are much too long; the wheelbase is different, and the frames would not even fit under the SD45.
- the MTH SD24 side frames appear to fit nicely as to dimensions and wheelbase; concerning the mounting points I could not see well enough for a definitive answer, but assume that
you will be required to do a little modeling. Very do-able, for sure.
The underlying truck "power block" for the SD9 is longer, and is an older design. The size difference between the double-clasp side frames for this loco and the SD24's is quite striking - almost a different scale.
eBay may yield the trucks that you seek, or maybe a dummy at a reasonable price. This
is a good way to build up your personal Parts Department - there will be future needs.