One of my Elka's also developed an oil leak about 18 months into ownership. I contacted Elka and they referred me to their only authorized service center in the US. The shop's price was somewhat high and the turnaround time was not all that great. So, I used my motorcycle knowledge and connections and instead used a local motorcycle suspension shop. The price was better and the turnaround time was good too. The Elka's are nothing special in terms of technology, in fact, they're pretty standard technology and any knowledgeable suspension shop can do the work.
An interesting thing (and not good) my local suspension guy found out was that Elka has some kind of issue or problem with these shocks. When he went to order replacement seals, Elka wouldn't sell the seals for these units, they would only sell the entire internal valving unit (called: the head). This is highly unusual, so my guy called them out on it (in a phone conversation placing the part order). The person at Elka would not comment and would only say that once the replacement head was used, then you could order seals only. This indicated to my guy that there was some kind of manufacturing defect that they don't want to discuss. So, if you have the updated shock head, rebuilding should be much easier, faster, and cheaper; especially if you use an aftermarket suspension shop.