So single pole, three position, non-shorting. It doesn't appear to have a spring return. Electroswitch doesn't offer single pole switches any longer, but you probably could substitute a two pole switch. Just use one pole and ignore the other. So Electroswitch p/n E2G0203N looks like it should work:http://www.electro-nc.com/rotaryus/e2.pdf
. Mouser says they don't have any. Digikey says it's non-stock, but they'll order one for you for $22.20. Allied Electronics also doesn't stock them, but says they'll order one for $22.25.
Antique Electronics Supply has something like the E2G0203N that might work: http://www.tubesandmore.com/products/P-SW50
. And it's only $10.50.
Here's an outfit that has what appears to be NOS Centralab versions of the E2G0203N for $9.95: http://www.guitarelectronics.com/product/SWL31/3-Way-Guitar-Lever-Switch-USA-CRL-Brand.html