lots of running around and trying all the hardware / farm / industrial supply houses
I got 2 S55 150 watt HPS and a 400 watt MH lamp NEW from a farm supply house
the date codes are from 2021

Try doing that here, the only lights I've seen for sale retail have been LED. 

Some stuff is already getting very difficult to find with a few things bordering on becoming Unobtaium.
Non-SOX LPS Lamps and Medium Pressure Mercury Vapour Lamps are 2 good examples of lamps that are sadly fading into obscurity.

 The more obscure the lightsource was in the past coupled with how long it's been since it went out of production , the harder it will be to find in the future .  The 2 you mention have both been long out of production so naturally they'll be WAY harder to locate . They are still around though and various members have found them rather recently . The more common stuff like CFL and Incandescent will more than likely be around long after most of us are dead and buried ! Assuming the world doesn't go stupid anytime in the near future !

there is also the other situation with CFL's unless people are removing AND keeping them there will be the JUNK FACTOR and people run them till they pop OR bin them early moving to the NEW "hotness"
I believe a LOT of incandescent GS bulbs were trashed with good life because they were "not good" compared and with such a SHORT life expectancy on "consumer" GS lamps there is a risk of them being unobtainable BEFORE linier florescent / Mercury and other "commercial" lighting lamps that would be bought and stored plus likely to outlive the luminaire they are fitted in (reno/ shutdown of business)

As said, depends on existing stock an stores willing/being able (regs) to sell it and where you live. This is a very *local* question with more than one answer.
For example, where I live, standard incandescent bulbs are already unobtanium since at least a decade ago, I can still get some halogens but it appears every place I've been to only has a handful of them and not all wattages are available.

These are small "mom & pop" shops where the owners already know me pretty much since I was a kid and are willing to sell me and their other long time customers (mostly seniors except for me lol) some of their stock they keep at the back, because "legally" speaking they can't do it anymore, if someone goes and asks for a light bulb they just sell them the standard noname LEDs everyone else sells, tho it's guaranteed they'll be back next month asking for another, quality is mediocre at most, we don't get Sylvania, Philips or anything from the known manufacturers, everything's low tier China stuff sold under local brands and if you don't like it cry about it, nothing you can do if you don't have a stash already.

I'd say around 2018 4ft fluorescents started becoming unobtanium, with 2020 being the last time I saw a new one for sale, and they were all 36W T8s. Never seen a T10 around and all the T12 I have were either given to me by oldtimers or scavenged from abandoned buildings, closing factories, etc. Shops I've mentioned might still have one but you have to be a known face to get one, otherwise you get "the LED talk" heh. Sparkies also replace the old fittings for all plastic LED fittings with aluminium wiring, ugh.

Halogens and fluorescents aren't strictly banned but ours is a market of "get what you can", we depend on what China or India have to export, currently that is LED, so you can't really find any previous technology anymore, that leads to people simply tossing away entire fittings in perfect conditions because you can't get replacement lamps for them anymore, mostly metal halide and fluorescent stuff... I mean, you *could* rewire them to retrofit LEDs but sparkies want to do their jobs fast so they just tell people to replace everything, which might be cheaper... I dunno, I pick up whatever I can find and repair/restore it to its former glory, some I resell some I keep or install at home. Got a whole box of used linear fluorescents we use, comes in handy to make the stock of new ones last a while longer.
There's a big basement here so I can afford storing fittings, bulbs, tubes, etc. My grandpa did the same, we still have incandescents he bought in the 80s, back then you could get much more, they're all Osram branded.

any lamp containing mercury is banned for import / production in my country and there are MORE floro lamps available NOW then last year as stores get rid of "dead stock" and so far zero "stuupid" price markups