Only ones still available I know of are ICS, G&G and WE who make a GBB one.
To be honest, handling an AEG L85 is going to be no help handling the real steel. By the time you'll need to fire a real steel L85, everyone else will be just a proficient and any muscle memory you have gained from using a GBB will be of no advantage by the time you have finished training. An AEG will be useless becuase it's nothing like the real thing, the weight is terribly off balanced compared to the real thing and with an AEG the reloading won't be the same. A GBB is only marginally better in terms of weight.
Your best bet is to get an AK because you like them. That way by the time you get into training you won't have any bad habits from using an AEG L85 and you won't have to unlearn anything like not releasing the bolt after changing mags etc.
TLDR; using an AEG L85 will gain you very little advantage, if any, and may even lead to bad habits, reloading, handling etc.