Every now and then heavy duty sewing machines come up for sale. They are able to handle about any upholstery job you can think of. They are even used by shoe repair shops for doing really heavy duty jobs. The better ones seem to be the German Pfaff units, although I have also seen HD Singers and Nechis. These units have a very large (close to MB starter size) motor hung under the work surface and are then belt driven up to the crank pulley. Foot control pedals, bobbin feed racks and all of the rest of the simple goodies are available, however don't know if such things such as zig-zag or fancy stitch options can be had or not.

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1961 190Db retired
1968 220D/8 325,000
1983 300D 164,150