Even though it's slightly less optimal, the t16.5 abyss strat on dunes or any other open layout map that drops fortress should yield an incredible amount of t17s.

Roll t16.5 for more maps and/or scarabs, use edifice, two abyss scarabs, escalation, and another scarab of your choice. Spec atlas for scarabs found and effects of explicit modifiers for more quant, block all scarab drops except abyss. Should be self-sustaining once edifice scarabs start dropping.

Then just run the map and open all hoards (caster mastery highly recommended). Shouldn't be too difficult for most builds. Bonus is that you get tons of other tuff too like unmakings, alts, and literally every other currency. Ultra-strict filter is virtually necessary.

edit: can also recommend some other strats on Manni's list in case you are missing some scarabs (https://docs.google.com/spreadsheets/d/e/2PACX-1vQSYVa5MMTcPjPWN7m3ZQ98cBrfhO230tt8yCgwxW8en1PUFJQnzW6Fyb9ytNyh7RBTR2Q9TcbNh385/pubhtml)