You could use a octaver pedall, that transposes the note down an octave, but pitch-shifting a full octave doesn't sound very natural and can be kinda slow to process..
I wouldn't want to muddy up my nice pure acoustic music with a weird sounding bass that a pitch-shifter would provide.

Honestly, I think you'll be much happier finding a cheap used bass somewhere. And you're probably in for a $100 or more either way you go.

Good luck.

Yeah, buy a bass. A used Yamaha, Washburn, Ibanez will be fine, get a beatup one, strip the strings, clean the fretboard and polish the frets with 0000 wire wool. Put masking tape either side of the frets when you do the frets perpendicular to the grain, and just give the grain a gentle rub, parallel to the strings. Check the electrics, resolder and fit new pots if necessary. Shield the interior of the electric cavity with tinfoil, glue it down. Put it all back together and you'll have something infinitely better than an octaver pedal. Or borrow one in exchange for giving it a cleanup and new strings.

Jeemy. I'm taking your advice. I found a Hofner acoustic/Elec bass for $75.00 locally

I'm picking it up on Wednesday!
THANKS ALL!

Kick ass. Post samples. CLEAN IT.

OOPS! I said Hofner.
It's a Hohner eab65 acoustic/electric bass.
I'll post pics when I get it and after I clean it up. :-)

Oh Yeah! I think you'll be MUCH happier than any pedal, and you got a great deal too! Congrats.

Go to Ibanezrules.com and look at his tech section. It gives detailed advice with pics on how to clean a guitar, except you obviously won't be taking the neck off. $75 sounds like a great deal, dependent on year these Hofners can be really great. An electroacoustic bass will be fantastic for acoustic music - it will certainly add a much more unique dimension to your arrangements than an octaver would have. So happy for you!