Don't know about Iowa, but the Minnesota Rifle and Revolver club's site lists a lot of Bullseye and other matches in Minnesota, Iowa and Wisconsin. http://www.mrra.org/schedule.htm
I know they have a Wednesday night air pistol league match in the Twin Cities.
I tried to find an air pistol match and I could not find one in Minnesota or Wisconsin so Jim and I decided to hold one on Saturday, April 1st at the Bloomer Rod and Gun in Bloomer, Wisconsin. But that is probably too far for you to drive. Besides regulation match we will also have a commercial SIUS system set up to run a seperate best shot or 10.9 competition. $2 for five shots. 100% of the entry fees will be paid out to the winner. Hopefully we can generate interest in air pistol.