The Catalyst catalog does not list anything that will fit in the Webplayer. However, if anyone makes such a product any time soon, Catalyst would be a top contender. Keep an eye on them.
The Webplayer has a mini-PCI type III slot, but many miniPCI cards don't specify Type I, II, or III. Mini-PCI is *very* different from Compact PCI, etc. It's pin compatible with micro-PCI, but won't fit the socket (Micro-PCI modules are sometimes soldered onto a slot card to make a mini-PCI card]
Unlike PCMCIA, Type I and II are *NOT* compatible with Type III - totally different slots and even form factors. See the URL below for more info.
I should also note based on my measurements of photographs of the motherboard (using the slot width as a calibration) The Webplayer should handle any Type III card. (i.e. Type IIIA and Type IIIB cards, which are identical except for the "height" above the slot socket. <50mm vs <60mm)
As far as I have been able to determine from researching mini-PCI suppliers, the only non-proprietary mini-PCI cards in production at present are modem, LAN, or combo cards.