You're right, at least, that this is what the prosecution will argue. The judge may even say that you should have subpoened those records in advance.
But by presenting the case law, and most every state has this, suddenly they ARE required to present calibration records. And since the prosecution has equal access to the case law (remember, you are a layman, and they do traffic cases for a living) the court should not grant the prosecution any mercy. The evidence against you (the radar reading) is in fact the prosecution's evidence, and they are required to substantiate it - not you. Broadcast this point well.
Here is a sample:
This can all be a lot of fun, if you let it. I lost my first trial by tipmra, because I was too emotionally involved - in my own case - couldn't think clearly, and got real angry at the judge who looked down on me as immoral scum. The second time I went for a lark, and even though I pissed off the judge by not following procedure - I objected several times to the cop's testimony (on basis of hearsay) - he got himself in on the joke, and I believe had some real fun with me in pointing out the prosecution's incompetance, and finding me not responsible.
Maybe you'll get lucky, maybe not. The worst is that you pay a ticket, but maybe have a good time "playing lawyer" anyways.