Don't give up on the AK90 yet!
You need to be aware that a transponder chip can only be programmed once and if the process fails the chip is then useless. Also the original key (on the e46 anyway) has a soldered transponder chip while the clone keys use one that is not attached to the circuit board (so the chips will have different numbers but they function the same).
Try the following seller on ebay from who I purchased e46 blanks. He was extremely helpful and knows what he is taking about. The listing below is for a blank mini key with new transponder chip ($69) but if you are just after the chip he could probably do that as well.
If the link is not active search ebay for seller artiway.