If you want dark rye bread, go to Werner's Oven @ Siglap. They
sell it there and it tastes heavenly.
Just so there are two types of corned beef on the market - one is a
canned version that tastes really weird and the other is sold @
delicatessens and tastes like beefy ham! I think the Reuben
sandwich uses the latter type.
You can get your dark Rye bread from Werner's and then go do your
shopping @ the Marketplace for the meats, cheese, sauerkraut and
dressing. But that will be very expensive.
The last I checked, Seah Street Deli sells this sandwich but it
costs well over 15 bucks.