Hey-Hey!!!,
Ebay seems to have a selection of Altec/Peerless line-speaker TX's. 15xxx depending on power and likely tapping options and perhaps distribution from 600R and 70V lines as well. Hunt 'Peerless' in the consumer electronics section. I have a feeling that the 600R:Voice-Coil ones would be best( if they actually exist ). More primary Z to improve te bass performance is usually a good thing.
regards,
Douglas