Catch-22 or maybe 23
I have read with interest the thread about replacement eyecups for the Nikon SE binoculars. There are other threads here in BF on this topic, including some lengthy rants by yours truly :-(.
My experience was as follows. I pursued Nikon fairly aggressively on the subject because, after all, the SE binoculars are premium models with a lengthy warranty. So the good news was that if I were to send the binoculars to Nikon (this was in 2018) they promised to make good on the situation.
But in this case, making good is perhaps not so good. They don't have any more replacement eyecups and they don't have anymore SE binoculars. So what they proposed to do was to replace my SE's with a pair of Monarch HG roof prism binoculars, brand new. I suppose some people would view this as a win, but I did not, and I declined the offer.
I don't know what Nikon's current policy would be, I mean, besides the very current situation that one cannot send them anything for repair at all because of COVID-19.
As I indicated in another comment, the best advice I have for people with still-viable Nikon SE eyecups is to treat them periodically with Armour-All and do not leave them folded up for long periods of time, i.e., when you put the binocs away always leave them extended fully.