Almost any type of audio recorder could be used to T-off the jack output of the radio receiver. Don't touch anything to do with outputs from the TOA amplifier. You may want to consider a recorder that has some form of automatic volume control if there is no human monitoring the recording process, but this could easily slip into the very lo-fi end of things.
Do you just need to record the person who has the radio microphone, or will you need any audience response or questions audible in the recording? Adding further microphones adds considerable complication to an otherwise single mono recording process, but if you are likely to have questions coming from the audience, you may need to consider this.