I haven't bought decals recently, so I don't know much about the providers or if they still are in business, but here you go..
What about http://www.abziehbilderservice.de/ run by Katrin Boehner, The heroic rider and winner in class 1 of the cannonball 2010 across US on a no clutch, single speed, belt driven 1907 JAP?! She said she put down very extensive research on the water decals she makes.
The link that Tim gave probably advertise decals from classictransfers.
http://www.classictransfers.co.uk/transfer-category/indian/?region=british-us&alphabetical=i-m
Pelders looks like they are still in business https://pelders.nl/
If you want a painted decal, maybe Hans Kreutzen can help.. http://www.paintdoctor.com.au/classic.htm
I think these guys maybe make some water decals, but also distribute from other providers water slide and vinyl transfers..
https://www.heortieg.com/indian-transfers-72-c.asp