Since you know and use Reaper I would render the song minus the bass track and move them to Reaper. I would use your MIDI guitar controller in Reaper. Using a DAW for recording is much easier then recording in BiaB IMHO.

Another option is to record your guitar, I am assuming you are a guitarist based on your MIDI guitar controller, playing the bass part then transposing that track down an octave. Sometimes that can sound as good as a bass guitar.

Also, again if you are a guitarist, go to Rondomusic.com and buy a bass. You can get quality instruments at a very good price there. I have a number of guitars and one fretless bass from them. The fretless bass is what you are hearing on my more resent songs and it only costs around $100 USD.

I hope this helps.

My goal this weekend is to move just enough each day so that no one pokes me to see if I'm dead or not.

64 bit Win 10 Pro, the latest BiaB/RB, Roland Octa-Capture audio interface, a ton of software/hardware