Your best bet would probably be to go through car clubs in the area. If there is a particular make of car that you are looking for, look in to that particular car club. Google will help :-).
The advice to google car clubs is excellent. I found a car club and emailed them for help. I found a gentleman to provide transportation in his lilac colored 1938 plymouth for my mother's birthday party.
I checked with my FI's coworker, and they borrowed the car from a friend. Her advice was to look up these clubs:
Exotic Cars (Osseo) MSRA (MN Street Rod Assoc.) Frankensteiners
I believe the classic car fair is coming up soon, and they display in the fairgrounds and also in Roseville at Har Mar. Maybe you could work something out with the owner if you find something you like.
Re: Vintage Car Rental
MY BMs in their dresses
Bio: Updated 1/02/10
Married Bio and Blog: Updated 7/25/2011
Knottie smorriso had a cool vintage car. It looks like she used Gary's Limo: http://www.garyslimo.com/.

http://community.thenest.com/cs/ks/user/default.aspx?UserName=SMorriso
Exotic Cars (Osseo)
MSRA (MN Street Rod Assoc.)
Frankensteiners
I believe the classic car fair is coming up soon, and they display in the fairgrounds and also in Roseville at Har Mar. Maybe you could work something out with the owner if you find something you like.
HTH!