There isn't much standardization among mechanical keyswitches, either: Alps, cherry, IBM, NEC, etc. all use different keycaps. Still, even a single company will be pretty inconstant in the Rubber dome (RD) world.
Nevertheless, some RD keyboards have similar keycaps to Topre. I know my Olivetti look a little similar. I believe someone on Deskthority found a RD keyboard with compatible keycaps.
One option is to get the keycaps off the RD keyboards, nad making a Jig for WASDkeyborads to etch them. maybe with some collaboration between you and him, you can get them etched or engraved with alternate legends. I am sure if you buy enough keyboards/keycaps, you can make it pretty worthwhile. If you make the jig close enough to the one he already has for cherry keycaps, WASD might not have to even change tho laser programming to etch or engrave alternate legends on yours.
Ofcourse, (In my opinion) the biggest issue is that the keycaps on the RD will very likely be ABS, and the legends will wear in time, though I suspect that if students have been using their bi-lingual keyboards for that long, they'll be proficient enough in either language.