In theory, these cameras are supposed to take six weeks on order from the factory, but you can sometimes find them in shops.
In my experience, the shop that most frequently has these cameras in stock is Fujiya Camera in Nakano Tokyo. I would say it consistently has more Pentax stuff in stock than Map Camera, including J-Limited models. I've seen them multiple times, but not always every colour.
At the moment their website seems to indicate that they have all colours in stock, including Viridian.
Link to their products filtered by Pentax Cameras:
PENTAX ??????????? ?????? ??????????????
The problem is that I think they only have a very little stock. So if someone happens to walk in and buy it the day before your friend arrives, it could just sell out and they tell you it's a factory order.
The other place I think they would have stock is the Pentax Club House in Yotsuya.
PENTAX?????? | RICOH IMAGING
But I can't say that there is anywhere you can be 100% sure your friend will find them. I guess he call ahead to see if they have one.
It might improve your odds if you can say your second choice of colour after Viridian. LX75 Metallic is very nice as well, but black is a bit of a let down in my opinion and Scarlet Rouge is a taste I haven't acquired.