Hey Bill -
Your login name is "laptaper" - are you recording on a laptop? If so, you might want to just consider running another channel and mixing them in post-production, using software such as Reaper. Ideally you'd like them to be timecoded together, etc., but you can manually match up multiple sources using time stretch functions within software to get the sources to match up to be in sync. Doing it in post will also let you experiment a bit to dial in the right levels, whereas in the field you'll be stuck with what you get that night.
The other thing you can do is edit the files in post production to boost the base, either using EQ functions or using a multi-band compressor add-in. The only problem is it will amplify all sounds within the targeted frequency, so you'll get more than just the base player.
There are a number of three channel mixers out there. To do the 480's justice, you'd probably like something like a SoundDevices 302 (
http://www.sounddevices.com/products/302master.htm). There are cheaper alternatives, however, since the 302 is likely $300+ dollars (just guessing here).
Good luck!
Mike
EDIT: Yowch!! After seeing Todd R's post, I took a spin through Yardsale and yup, a recent sale looks like it went through in the $1,200 range. Guess that's not such a good option....