Need Advise – WordPress & Metered Content

We have a small newspaper site that were are looking at rolling over into a metered access type setup. In other word give users a certain number of free article/post views per day/week/month then once they hit a threshold they are prompted to pay to read further.
I have been having trouble finding any plugin or service that provides just the metering support for WordPress sites. There’s plenty of paid membership plugin providers just not seen a metered access plugin/provider.
Does anyone have any idea where I might go for this type of thing? I’m not opposed to purchasing a plugin but I haven’t even found a pay option yet either.

Thanks for any help!