Unless someone makes a third party run again (I did have one back when, still do actually, thing overheated a lot but different story there) or maybe an open source version (never looked into how difficult it might be actually, though equally given half the fun I have seen for region changing, flash carts, controller fixes and RGB video out on the N64 that nothing like that has crossed my path presumably says something. Might pull apart my old one to see what is in it) then as they are required to play several of the best games on the N64 ( https://nintendo.fandom.com/wiki/Nintendo_64_Expansion_Pak with improvements in many others) and for the most part have no downsides to leaving them it is not going to be like extra controllers someone might sell from time to time if nobody else is playing with them such that the market has enough supply to drop prices.
At this point you would almost be better off buying lots of second hand N64s in the hope that one has one and the seller did not know (unlikely compared to what it was like back when as most people flogging them tend to know what they have) or is otherwise giving a good deal, swapping out for yours (or keeping it if it is a nicer model) and reselling on (depending what controllers and games you get you might even be able to make up better sets for someone to have that two player off the shelf goldeneye or whatever experience, or even go into the whole RGB thing).