You can DIY, check Vaughn's many incarnations.

You can buy from many of the Hong Kong ebay places.
About 15-20$ US.

You'll need the KH ref solution and bromo blue pH indicator. Add 3 drops to 6mls of KH solution inside the drop checker, replace about 2-3 week intervals etc.

Getting the KH ref solution will be the tough part unless you or others "Down Yonder" there make it.

Regards,
Tom Barr