You can find a piano midi file of "In The Sweet Bye and Bye" with right hand chord melody here;
http://breadsite.org/classic.htm"In The Sweet Bye And Bye"
The second one sounds pretty good to me. Right click on it, save file as, MIDI sequence, save in where you can find it.
Open it by itself in RealBand, transpose it to the key of your BIAB version and set the tempo to match. Insert bars at the beginning so it starts to match your BIAB file. Save it as an SEQ file so you don't loose your edits. When you want to try it against your BIAB version export it as a midi file as one midi track. Save it with a different name such as Sweet92bpm88bars.MID, import that into the melody track in BIAB. From there you will see what changes you need to make to either the SEQ file in RB or changes you your SGU file in BIAB.
That should get you started if you choose to do it this way.