How much higher do you want your bars? There are 4 basic ways to go:

New stem - easiest swap to make.
There's the adjustable stem route - $30 and they'll get you pretty high, and you can adjust lower if you want in the future.
Here's a pretty tall 1 1/8" stem - $10.47 No faceplate, so you'll have to strip controls from one side of bars to swap stems.

New adapter + stem - offers more stem choices, fairly easy swap, but not as easy as stem alone.
Hey, whaddya know, I found an adapter - $16
Then get a 1 1/8" threadless stem with a clamp diameter of 25.4mm. $12-$100. There are many to choose from.

25.4" is becoming more rare by the day, so you may want to consider a 31.8 stem and 31.8 new handlebar as well - kinda crazy to spend like that on this bike, though.

New Bars - more work than a stem swap as you'll have to move grips and controls from one bar to another.
Maybe some 90mm riser bars would work? - $18
Maybe those aren't high enough? Go Wald 869 ape hangers - $15

Overkill - getting a new threadless fork and stem. too much expense compared to overall worth of bike, IMO.