According to bikepedia.com, your shifters are
Shimano EF65 8 spd trigger
Now bikepedia certainly isn't infallible, but you might Google the description and see if those seem to match.
IF you broke the right shifter AND your bike is an 8 speed, maybe you want to upgrade to 9?
In addition to the shifter, you'd need the cassette & chain. You can get those for around $60 for the lower level version cassette and decent chain.
That's probably about what the shifters are going to cost online.
I recently upgraded my ride and the integrated trigger/brake shifter was actually very similar in price to the non integrated one.