They are not any more-or-less rare than the other Meucci Special Edition cues. They were/are all made in the same quantities (500 for a few of the earliest ones, 750 for some, and 1000 for some), though some of the newer ones haven't yet had all 750 (or 1000) made.
In fact, the Meucci SE-7 would be twice as common as the others, since there were actually ~2000 made in total. 1000 with a forest green stained forearm, and 1000 with a walnut stained forearm.
NOTE: I've not confirmed this with Meucci. I make this statement based on the fact that I've seen #899 in both versions, leading me to believe each version may have went all the way up to 999. but Meucci is notoriously BAD at keeping track of things, and often duplicate, skip, forget, or just plain mis-number their cues. It's so bad that you just can't really trust serialized runs from Meucci. They can only really give rough ideas of how many were made for this reason.
They are out there, and I see them come up for sale from time to time. You just have to keep your eyes peeled and know where to look.
Meucci Collector Facebook groups would be the first place I would go. Use the search once you join the groups and see what you can find. If you don't find one posted already, create a post and ask if someone has one to sell. You can usually find cues this way.
eBay and other classified sites are also good. If I'm looking for something specific, I typically create alerts on those classified sites so I get notified automatically.
The exact Meucci SE-7 in the earlier question you linked above went up for sale in 2018 for $950, didn't sell, then was lowered to $799. It was described as "Unchalked, in 'new' condition, with 2 matching shafts".
It didn't sell at either of those prices.
I think $800 was a few hundred too high. It does have more value, given that it's brand new and has two shafts. But a non-sale indicates it might have been a bit high.
It is still for sale for $750.
You also pay a bit of a premium for low serial numbers, specifically "000" or "001", but I don't think that applies here.