JTC,
Sadly, Shure has discontinued all VHF wireless products and no longer supports your wireless for repair or replacement parts. The old Shure LX stuff really worked great as long as there were no RF interference in the area.
You could find another transmitter on ebay if lucky, but otherwise save yourself the aggravation and just go buy a new UHF system. Do not buy anything used that is in the 698-800 meg frequency range, it is totally illegal to use them.
For a good value, look at Audio Technica's 3000 series systems. They are rock solid and the mic sounds very good. If you can find them the Electro Voice RE-2 or a used Telex FMR-500 with either the N/D 767 or the RE410 mic capsules are awesome values and sound boobies. Advantage to the EV/Telex system (they are the same system, different silkscreens) since they still have an rotary gain pot to really set your mic up to your voice's strength. All the AT and also the Shure systems are only adjustable in +6 or -6 db increments. It gets you close, but who wants to be close? I want it optimized! Go EV/Telex if you can find them.