Is there an extra monitor feed coming from the stage snake...?
Depending on the scale of operations and your access...you might be able to get a suitable feed for a matrix from the monitor mix...and then use your mics close or on-stage...
This is the best answer. Ideally, you want to run mics within 10ft of the stage if you don't have a delay unit. If you can't get the mics that close to the stage, I've tried 3 alternatives:
1)
Mix mics low. If you mix the mics low enough, the delay sounds like natural reverb, not screwy echo. This requires a mix of at least 85%/15% for the board mix, so if the reason that you want the matrix in the first place is that the PA mix sucks (like it's vocal heavy with little or no bass), then this is not a solution because what you'll get is the board feed with a little added warmth. If the board feed is reasonably balanced (in the sense of all the instruments and vocals at reasonable levels, not balanced like XLR outs...), you can get a damn fine recording this way, but this ONLY works to make a good board feed sound great, not to make a shitty board feed sound good.
2)
Separate tracks. I have dealt with delay in the past by panning the board feed to one track and the mic feed to another (like board R and mic L), and then I removed the delay from the mic feed in Soundforge after I loaded the DAT onto my HD. You can get a good recording doing this as well, but the main drawback is that the final mix will be mono, not stereo.
3)
Try to separate ranges. This is the toughest to do, and I'm not even sure you can do it with a UA-5. What I've done in places where the PA feed is OK except that the bass isn't mic'd is to crank the bass and cut the treble on the mic feed and vice versa on the PA feed. The idea being that if the bass is strictly from the mics and the higher ranges are strictly from the board, then there aren't any overlapping ranges where the delay is noticeable. Of course, this requires that you have a mixer that allows you to do this. I'm not sure if the UA-5 does that. I've only gotten mixed results from this method of matrixing, mostly because the mix in the board feed wasn't very good to start with in the places I've tried it.
If you want to get a delay unit, the one I've seen used in the field is the TC Electronics D-2, but I'm not sure what is the ability to use this without A/C available. They run about $500. Good luck.