Is there a more sustainable way to enter it?There is.
- To the south from don's hideout, there's an area with hobos. One of the hobos tells random advices when fed. You have to make him say about the fake passes; if he says something else, sleep and ask again, it resets him.
- After getting info from the hobos, go to the slums market and find the guy selling junk; when asked, he would reveal that he's also selling fake passes.
- Game randomly picks which of 4 passes is correct, with other 3 getting you arrested. It resets if you get caught or if you pass successfully. To avoid headache with it, go to Lin Lin (masseur) in the slums area, and do massage with her (after getting fake pass); she would notice fake pass, and, for a small fee, tell that local tattoo master can improve these for a price. I think she wants 100 credits.
- Owner of TAT2 salon demands 500 credits to fix any pass. Do it once to get one copy of a good forgery. Now, as long as you keep at least one good pass (don't waste them all), you can use tinkering mechanic at home (Cassie's safehouse, Condo or Milk Farm) to mix bad passes with ink pens and make good forgeries by passing medium-difficulty Nimble check; even if you fail a couple of times, it's still cheaper than doing it through TAT2, as it's 102 credits versus 600 for one copy.
- Now, just pass checkpoint. Make sure you deequip weapons and dress "decently".
Even with tinkering I lost lotsa money to collect the onesies, doing quests there and visiting the island.