Look for a Bausch & Lomb Balomatic 755/756. I found one locally with trays, and the colours when projected are just stunning. The whole kit, all clean and well kept, cost me about 150$.
You could always hunt for more advanced stuff from Hasselblad or Rollei, Cabin etc, but you will have to be ready to invest more.
Also, try Ektachrome 100VS too. It's Kodak's equivalent saturated-colours slide film, and while it does not have the same look as Velvia, it has beautiful colours, rich and vibrant without being over the top. Plus, it's very good on skin colour.