Selecting small rivet size

[dmjlambert]

I'm working on my A/C evaporator box. I drilled out the rivets. The work thickness is 1/4 inch, the work hole diameter is 5/32 inch, the old rivet is 1/8 inch thick with a very thin and flat head. What is the proper rivet to use? I don't know what length to pick that will ensure the tube will curl and flatten nicely and properly hold. Can you help pick rivets or does anybody here have some that are proper?

The rivets GMC Paul sent me for my vent window rubber replacement job were too long for some parts of the vent window. The solid part of the rivet was too long and no matter how much I pressed and hammered the rivet it would not hold snug. I had to drill the tube part of the rivet to be deeper. I don't want to do that with whatever rivets I pick for this. Do I need to go 1/8 inch longer than the work thickness for the rivet length, or is there another number?

I need to find about a dozen rivets for this. I still have the special punch from GMC Pauls, or I was thinking of getting one of those Corvette Aero-rivet tools or borrowing one from one of you fine folks. I don't like pop rivets. #8 or #6 1/2 inch long machine screws with an extremely thin head would also work, but not having great luck finding something with a head about as thick as a rivet head.