I think all the alolan variants are available as of this time. If looking for one specifically you can always ask in on the hunt about it.
Reborn has unfair difficulty? i disagree, the difficulty is fine, it seems mostly like the people who are reliant on Pokemon that are their favorites or are KNOWN for being incredibly strong in the main games and don't want to use a strategy to counter their struggles are the ones saying reborn is way too difficult. Name one part of reborn that is unfairly difficult, or one thing, every episode Ame carefully places Pokemon where they are best put for that progress of the game and sometimes tweaks where existing Pokemon can be found, but all of this is to inspire people to use things they would never use before and to give them a reason to try multiple playthroughs with different Pokemon, in fact it is dark souls that i would say is unfairly difficult and the community for it do not help in the slightest given if you seek help for it you will only be told to get good, which helps no one but that's another topic. The point is i have not seen one single part of reborn that is so difficult it could be considered unfair.