Of the papers I've tried, Forte's Polygrade V RC glossy seems slightly glossier than others I've used (Agfa MCP 310 RC, Foma Variant 311, Oriental Seagull VC RC, Kodak Polycontrast IV, and Ilford MG IV). I've not tried the Adox or Maco papers mentioned by others, unless they're the same as something I have tried under another name. FWIW, the Forte is also the coldest-tone paper of the ones I've tried. They've got a warmtone variant, but I can't be sure it's got the same extremely glossy look to it.
Speculating a bit, I bet there'd be a way to increase the glossiness of any paper by some post-processing coating. Maybe a spray-on lacquer or something along those lines. I've never looked into such things, though. Maybe you could peruse the B&H, Adorama, Freestyle, or other Web sites or ask at a local photo shop or art supply store.