Replacements are not so difficult to get hold of. Genuine article costs more than a standard one that works though. Use a search engine on the Net. Or go to a local DIY shed to get one that you programme by entering the ID of your TV.
Is it a SKY+ remote ? If so, then you may need to re-tune it via SKY customer service. Did this last week. I think this caused by not replacing the batteries in time with the new ones. You need to replace new batteries within 10 mins of removing the old ones.