Basically any gaming adapter, bridge or router running in bridge mode will work fine, so long as it plugs into the ethernet port, not USB (only panasonic's USB wifi dongle works in that case). The latter is usually the cheapest option. I use an old router running DD-WRT firmware. Tomato firmware is another option. That turned out to be free in my case. Bridges and gaming adapters typically run $40-$100, or much less if you by used or refurb on ebay. Power line adapters are another popular option that works well.
If it turns out you can only find an expensive solution, you may as well buy a new player with wifi built in. A Sony 570, for example, which is wifi with netflix goes for $50-$70 on ebay these days. Personally, the black flashes on netflix on the 110 drove me crazy, so I was happy to get rid of it and get a better player.