joney:
I just answered this for you in a visitor's message, but it is a good question and I will again answer it here.
-Nick
Answer for all:
Yes, I know of (and created) the software to convert .prc to .rb; it's called Mobi2IMP and can be found in the thread
Mobi2IMP 9.4 with new Windows GUI & UTF-8
You will note that there is an option to convert the .prc/.mobi/.pdb file directly to REB1100 .rb along with the .imp for the EBW1150, namely:
For .LIT to .rb, follow the instructions (again created by me) to convert .lit to .imp as per the thread
Convert .lit directly into .IMP formats .
Then ensure you have created that empty file 'debug' so that the .html and images are left behind. Open the o_sb.opf with eBook Publisher and choose as the Build Target 'Monochrome Half-VGA'.
Happy converting!