I can't seem to find this anywhere in the US right now for some reason, but I've got an older model where the receiver is more like a guitar effect pedal, but it works great. You just plug it onto the end of any mic and voila, you're wireless. He could still use his Beta and get to be wireless as well.

Here's the website I got the info from, it's in the UK...
http://www.thenoizeworks.co.uk/
Samson Upgrades Airline.
Samson's new Airline 77 plug on wireless system now features Audio metering and a swanky new carrying case. The systems features an XLR sized plug on transmitter which you can plug onto your favourite dynamic mic to turn it into a wireless system and we have lots of options available including Beyer TGX60/80 or Shure SM58/Beta 58 systems. Just for good measure, the system now comes with Samson's own excellent Q7 microphone. Available in 4 UHF frequencies.
Good luck.
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Douglas 5 string, Nady MGT-16R Wireless, Korg Pandora PX4B, that's all it takes.
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