Newbie wants to buy one Luger

I used to collect military weapons 20 years ago. I sold everything in 1991 to finance grad school. Now I'm starting over. My plan is to acquire one each of the major military handguns used during WWI and WWII. My question is where I might find a reputable collector/dealer to sell me a Luger. I'll gladly pay fair market for an original/correct pistol and I'm not picky about the mfr. or model. I know my way around 1911's but not Lugers and don't want to get burned. Any ideas? All help appreciated.