scheels in coralville might be your best bet
If that's his best bet, he can prolly get as much in Minneapolis, and it's not going to be inexpensive.
For inexpensive, if you're cutting out at Mason City and jumping on 218 (which I'd recommend over coming all the way down to 80 on 35, I have in-laws in the TC), locally here in the IC area, there's a TJMAXX in Coralville as well, and they do have some ISU stuff. Ain't been in there recently, but I know the wife got something for our 2 year old last year or the year before.
Another option, depending on when you're getting in town, if you can stomach it, I heard the Fry Fest will have ISU vendors. Not sure if it'll be cheap or what they'll actually have, but they've been saying it on the radio that they're having ISU vendors.
Links for more information on Fry Fest:
Map:
Location & Map - FRY fest
Schedule: (looks like 10 AM to 8 PM is the tradeshow...assuming this is where the ISU vendors will be)
Schedule of Events - FRY fest