Best script/service for conversion tracking?

I know this merchant who's got an affiliate program which doesn't support subids, so I have no way of knowing which kw's convert.

I'm doing direct to merchant ppc, and maybe other traffic sources too. The merchant offered to put some tracking code on *their* thankyou page and is waiting for me to provide it.

If I go w/ Google Conversion tracking then it only works w/ Google AdWords, right?

So what's a good script I could install on my own domain and that would produce some code for the merchant to add to their ty page? I'd like reasonable reporting and kw cloaking.

I looked at prosper202 and OMS/OptimizeMySite but they seem better suited to landing page affiliate marketing.

Any suggestions?

@hyperion thanks for your referral link but who wants to join another membership site to pay some monthly fee just to get some script that is barely explained?

Besides there's no way it would work w/out the merchant dropping a cookie/pixel for me. I'll poke around prosper202 and there's always hypertracking.com I guess.