Just saw your request for where to buy the trifold blind rivets, I get mine at a RV surplus and salvage place but they are available online and at various stores like, Fastenal. It would be best to do a search on Google(or your favorite search engine) for trifold blind rivets or pop rivets.
I'm not sure about drill size for drilling the rivets out but there may be a piece of the shaft that goes thru the rivet still inside the shank of the rivet. Sometimes you can drive those out with a pin punch, sometimes not. A I/8" rivet uses a #30 or 1/8" drill bit there are several sizes of rivits and naturally they used sifferent size drill bits. I sometimes use my dremel tool to cut the head and sometimes, like in soft plastic I use a small hole saw intended for removing broken screws from wood. You just have to be careful not to damage the skin of the MoHo.