Have you tried getting replacement parts from the U.S. Ventus supplier?
They are:

    Organ Supply Industries
    Box 8325
    Erie, PA  16505-0325

    Phone: 1-800-374-3674.

I also know of an organ blower manufacturer in the Lansing, Michigan
area, the name of which escapes me (I'll ask around and post it when
I find out the address).  You might also try the old-timer in the
industry, Spencer Turbine Co., Hartford, Connecticut (I know that
they're out of the organ blower business, but one of their stock
"turbo-compressors" might meet your needs).  Also, W.W. Grainger might
have something, but those are industrial blowers in their catalog, and
may need a lot of help to make them quiet enough for church organ use.