Finding a diesel cluster that matches your Immobilizer shouldn't be that hard. If you have a 2003 car, then you have an IMMO3 car, which means you can use the 2004 clusters in this style because they are also IMMO3. That would remove any cost for deleting the Immobilizer.
Since this thread was originally created, you can now get the SKC using a free tool:
So I've been a happy VCDS user since buying my Golf in 2003 (it had 65000 miles on it so it conveniently needed an immediate timing belt replacement, hence needing VCDS - though it was named VAG-COM way back then). However there are things that VCDS doesn't do, such as pulling the SKC from an...
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And, if you pay $15-30 for the appropriate cable, you can use the free VCDS Lite to do the pairing.
I don't know if this next statement is true, but if your current cluster and the replacement cluster are from the same manufacturer, I think you might even be able to clone your EEPROM from one to the other, and then you wouldn't even need to pair anything. Someone else here can probably verify if this is true. I know this can be done like-for-like clusters.