slow request

I need something in around 67 BPM ballad-esque with lots of slow bass guitar. My bandmates have been working on a song that keeps changing, measure by measure, randomly, from 65 to 69 BPM. It's my job as drummer to get the beat nailed down to a specific tempo (probably 67, since that is the average.) They gave me a recording of the song to work with to come up with a beat, but because of it's randomness in tempo between individual measures I can't come up with anything because every time I play along with the recording, I end up off from the song I'm playing along with so nothing sounds good.

I basically need to have a drumless track like this to play along with with a consistent tempo to help me come up with ideas and beats that I might apply to the off-tempo song my bandmates are playing.