Here’s a surprise! An alphabet of “Moultan or Wuch”, found in a large, dusty polyglot bible, found at the William Carey library of Serampore College, Kolkata. The amazing Archive.org has a copy of the entire book scanned and available for browsing/download. A huge file, but possibly an excellent resource for script researchers!
As Chris Miller has noted in the comments, script researcher and activist Anushman Pandey has included a wealth of information about the script in his Multani unicode proposal. Be sure to take a look!
By the way, here’s a brief intro to the Landa scripts via Wikipedia. The Landa scripts were unconnected scripts used by mercantiles, i.e. for quick, informal handwriting.