I managed to find a nice little period (sort-of) speaker for the SW-3 receiver on eBay. It is a nice little "tombstone" style cabinet with about an 8 inch speaker and impedance matching transformer. Presents a nice high impedance to the receiver and the pin connectors exactly match the connectors on the SW-3, so it plugs right in.
The cabinet is cast metal (likely "pot metal" (zinc)) and is quite brittle, though the exterior condition is quite good for something as old as this is. However, as is the case sometimes with eBay purchases, it was unfortunately damaged in shipment and one of the corners was broken off. The seller did right by me and refunded 1/2 of what I paid for it and so I kept it. Fortunately, the damage is on the back and relatively easy to hide from view.
The speaker works admirably with the SW-3 and I enjoyed imagining what it was like in 1930 to be listening to this little rig whilst running off batteries. There was a lot of activity on 40 metres as this was a contest weekend, so there was able listening material along with the 49 metre broadcast band.
Last evening, I changed out the frequency-determining coils in the SW-3 and tuned around the 80-75 metre band finally settling on 3885 khz where a group of AM enthusiasts was parked holding a round-table discussion on everything under the sun for hours on end.