There are a lot of claims about the "best Zappers" so it's really hard to figure on one when nobody has any studies. Here's some pros and cons -
The $10 model is the only Zapper that uses cmos circiutry, (which makes it unique), it's the very smallest and in my modest estimation, the easiest to use. The size makes it very good for traveling. The only short comings I can see here for you are that it does not have an on and off switch, so you have to unplug the battery after use - or an LED light (the battery does last a lot longer though because of the cmos) and it's not super fancy looking.
ParaZapper has lots of accesseries which you may be intersted in, and some fancy looking models, probably your best bet for a super one, though you may or may not have any better results.
If you end up with a terminator for some reason, the worst thing you can do is Zap 24/7, it doesn't get all the parasites that way! (I strongly believe) - Not that it's damaging to you, but you need to have the breaks and the right voltage to get them all. It seems good for applying to specific areas though.
I saw some pretty cool looking Zappers, very cool at http://frequencygeneration.com/ but then again, your up against the copper pipes, which are good, but inconveniant. - So, I would swap the copper pipes off (they have gater clips, so you can change electrodes) for some finger rings (my preferance) or some accessories from Paradevices.