I think I drove past the building that guy in Friendship has a couple of years ago.  I was thinking he is more of a "loader" than anything - buys brass, primers, powder, bullets and makes rounds.  There is a guy up in Medford who gets a bit more exotic.

Hitting out of the way places does seem to work ok - I wiped Dorn Hardware in Madison out of Japanese cartridges and, when he went to reorder, I think he found out why.  That was probably kind of lame of me.

If your father is the auctioning type have him go to the local estate auctions as they're a good source for older cartridges.  Off the top of my head Dairyland in Kendall, Gavin in Baraboo, Kramer in Prairie du Chien, and Auction Specialists in Mineral Point tend to have gun auctions with old ammo.  You do have to be careful about reloads but unfired/unopened boxes hit the blocks frequently.  Prices tend to be a buck a round or less.  I pretty much get all my .32 Remington that way.  I also buy Krag that way so he'll be bidding against me.  Just have him attend the workday auctions as I can't go to those.

Cheers.