I put Lace Alumitones in one of mine. http://www.lacemusic.com/
If you want to upgrade the electronics look here. http://www.stellartone.com/ToneStylerBass.asp
I have two of these in the one with the Alumitones.
They also have a dual tone pot that isn't a ToneStyler. It's called a DuoTone and is a tone pot with two pots on one switch. Not currently listed n their website but they have them and are about $20. I put one of these in my other Jag SS.
I'm sure there are less expensive options, and you should get many options. But this is what I have in mine.
My grandson isn't really an Elf, he just plays one in videos.
Club Member of Guild, Tricked Out Squier, Hagstrom, Squier Jaguar SS, Short Scale Bass, GK, Gretsch, Vege, Thunderbird.