Hi R999,
I've heard good things about the Hanna Checker ph test meter on the forums and it sells for around $40 and I found one online for $34.95 here:
hXXp://www.bghydro.com/BGH/itemdesc.asp?iC=TEMPHHAC1
You may also want to start thinking about getting a meter to measure nute strength (tds - total dissolved solids) and you can get one meter that will do both and in the long run it could save you some $$$.
I've used a Hanna 9813-0 Combination ph/tds meter for about 12 years. The 9813-0 is a combo meter that tests nute strength (tds) in addition to ph. It has a waterproof electrode 'wand' attached to a heavy duty cable that is separate from the main unit. I've found that this is a much better design for me because I've had small hand held units that I've killed by having it slip out of my hand and fall into my nutes!
Oakton makes meters that are waterproof and they float if dropped in nutes. Another great thing about having the electrode separate is that you can replace just the electrode when it goes bad in a few years instead of replacing the whole unit.
For me, it was worth it to spend a bit more and get a more me-proof unit. The 9813-0 usually sells at the local grow shop for around $200. I found a great price ($159 w/free shipping) at this website and they have tons of meters:
hXXp://www.eseasongear.com/
Even suppliers I've used that match any price didn't want to touch that price so I went with eseasongear.com and everything went smooth and it was shipped very quickly.
I'm sure some other MP growers will chime in with what they use but you may want to consider biting the bullet, spend a little more and get a meter that will test for ph and tds and will be around for a while.
Good Luck!