The cold plate breadboard holes are indeed 4-40.

I've installed a new o-ring and vacuum valve, but I've scoured the labs for any piece that fits the open port on the side of the cryostat and have come up empty-handed. I've attached a photo with all of the IR labs input pieces found thus far (except duplicates or ones that match these same dimensions), none fit the drill pattern or counter sunk hole of the cryostat port. I tried but could not find mention of this specific port's removal in the elog history. 

Spent a while trying to make a Franken-stat from the innards and limbs of the other decommisioned IR lab cryostats but nothing allowed for a correct optical path. So I then started to make a custom port with a 122 o-ring and an old ISO blank flange, but I need a drill bit larger than 0.5" for the center electrical feedthrough and am having ID card issues accessing the student shop over in CES.

I will call IR labs tomorrow and see if they have an a standard piece for this feedthrough.