yeh you can do it pretty cheap if your prepared to do a bit of legwork and DIY.
Get yourself a used fob, two or three button will work fine, ebay is your best bet here, you can get them for around 20quid if your patient. Alternatively, find someone breaking an A4!
Blade cut to fit as mentioned above.
Then you'll need vagtacho to pull the SKC from the cluster, and program the new transponder.
I reused the immo transponder in the used fob when i did mine, it recoded just fine.