A quick Google of the speaker model makes it appear that they are analog 900Mhz stereo. While the analog 900Mhz stereo is common, the exact specs and frequency can still vary from mfg to mfg, but it would surprise me if they varied that much.

The older, and hopefully "maybe" some of the current speakers, from Radio Shack and RCA used Analog 900Mhz Stereo and their speakers were compatible. If you can find a transmitter with a variable transmitter frequency control, which those did have, it would probably be your best chance of compatibility - but then there's no guarantee.