If you can't find an adventure, I suggest using the Plot Map method from TechNoir.
Basically, you make a 6x6 table. 6 NPCs (usually PC contacts), 6 items, 6 locations, 6 events, 6 factions, and I think 6 rumors.
Roll a few random items from the table (you should make the funny money as part of the seed.) Link these beginning items together. Maybe Faction1 is spreading the fake cash to frame Person6, because he stole Item3 to empower Faction4....
Anyways, you'll have the first threads the PCs should investigate, so you set the hook to point them to one of the nodes.
Now, whichever step the PCs go in, they'll get some information. Where it leads is RANDOM! Roll on that big table again... Event2....Faction4 is planning to test the item during the event. PCs rush to stop the test, they corner a faction4 goon. Roll on the table... He has heard a rumor2 that person3 has a counter to the item! The PCs try to track him down, but he has been event6-ed! On and on and on.
The book explains the process better than I can. And learning the process and populating a table with 36 items from your campaign shouldn't take much longer than reading through and prepping an adventure.
Then you'll have an entirely new game and a process that can be dropped into any investigation game. I once used it to run an improvised game of Spire the City Must Fall. I just filled in a 6x6 table, generated a starting seed, and away we went.