Yes, putting the pump in your pond is the best bet. It occurred to me, if you are leaving soonish, and leaving this terrarium for someone else to care for you may want to skip the water feature all together. Even if you don't have animals in the viv, you will still need to do water changes from time to time otherwise the water will turn brown with tannins and/or green with algae, and will eventually turn into a stinking mess.
Sorry to backtrack a little, the exoterra bulbs aren't necessarily bad, they are just way overpriced for what they are because they are "specialty animal" bulbs. Any fixture that will hold a screw in type bulb and keeps the bulb from touching the top of your terrarium will work. Try searching for rain gutter fixture or the like to see a simple DIY fixture that would work well for what you need.
It is up to you whether you want to use an aquarium or a manufactured viv. An aquarium would be cheaper and less likely to have water leakage issues over the long run if you did do a water feature. The manufactured vivs are nice because the front opening doors make it easier to access to service, you don't have to take the lights off the top every time you need to open it. You would probably want to replace or cover most or part of the top of an exo/zoomed with glass to keep humidity up if your trying to grow mosses and such.
I'm not trying to be rude, but please use the search function and look over a couple build threads similar to whatever you end up deciding to build (with or without water feature). It will help you figure out how to build your terrarium and what materials your going to need.
One nice thing you don't have to worry about in a plant only terrarium, you don't have to frog/fruit fly proof the false bottom, doors/lid, and vents like you would with a viv housing animals
