Hi Jaap,
Today, I took delivery of an HM Digital PH-200 pH pen. Please take a look at:
http://www.tdsmeter.com/products/ph200.html
It is too soon to say that I made the right choice - so watch this space!
When you say 'reasonably priced', what did you have in mind? It has to be said that pH meters are, by their very nature, complex pieces of kit. It is possible to pay very little for a pH meter but its accuracy is not likely to be particularly good. If, for example an accuracy of +/- 0.2pH meets your needs, then select one accordingly. If auto-calibration is important to you, then add that to your requirements specification. Also, be aware that the sensing part of a pH meter - the pH electrode - may give you just 18 months' service after which it will need to be replaced. So, choose a meter that will enable you to do this. If you take a look at the above link, it will hopefully give you some ideas of what you need to consider.
JPC