I don't recall offhand which O-rings are in my flight tank at the moment.
https://www.marcorubber.com/o-ring-chemical-compatibility-chart.htm#chemId=1483
Check other sources as well. This was just at the top of the list of a quick google search.
Keep in mind you also want your o-ring to be able to take some temperature excursions. For instance when the nitrous goes from the pressure line to the unpressurized tank, it starts out somewhere around -130F IIRC before repressurization.
https://www.nes-ips.com/o-ring-for-low-temperatures/ but look for additional sources of info.
https://www.rocketseals.com/low-temperature-o-rings-and-seals/ This one caught my eye just because of the name!
When I designed THRP-1 I didn't pay enough attention to thermal + pressure shock in the flight tank. I use chilled nitrous but not low enough to cause any issues with any O-ring materials in that regard. But flash-freezing an O-ring while pressurizing could possibly lead to cracking - and that would be bad.
However I have had my tank pressurized / depressurized a few times, and aged a few years, between disassembly. The O-rings were still perfect. I just don't recall offhand what ones I used. I might have re-assembled it with the same O-rings. I don't recall that either. Sorry! And it's too late for me to want to dig through my records.
Your grease for the O-rings definitely absolutely - I cannot stress this enough - MUST be compatible with nitrous oxide. There is only one manufacturer choice here, that I know of (and I'm probably wrong about that). It is expensive (that I'm not wrong about). You don't need to use it around the nozzle end but IMHO you definitely do need to use it on the flight tank etc. Krytox has gotten expensive. There are multiple versions. I'm not sure we can get our hands on the aerospace grades. I'm using 206 because it was what I could get when I needed it last time around. Others who have researched it better might be able to give you a better recommendation.
But in any event, you definitely do not want to be using incompatible grease. Nitrous Oxide is a good solvent, which is not one of the properties we're normally thinking about. It will dissolve some hydrocarbons and organics just fine, including some types of grease. Then N2O + hydrocarbon contamination = explosive. It won't take much to make it rather more sensitive then you want to be messing with.
So consider the grease has to be safe with pressurized oxygen (that's part of what you get if the nitrous starts to decompose for some reason), safe with Nitrous which is an organic solvent, safe over a wide temperature range, and safe with your O-ring or seal material of choice.
Gerald
PS - IIRC, the Mobile 1 was for the outside of the fuel grain. Not for the O-rings that get exposed to nitrous oxide.