Since I had already laid out a lot of $$ for the rest of the set up, I ordered the cheapest mouse I could find off the Dell site and it works fine. It was less than $10 delivered, but I don't recall the exact price. Mine is a wired one though (USB) and wireless will cost you more.
Also, congrats on the successful install. Be sure to post in your other thread that yo got things working (and how if you can recall) so others can maybe see what works too.
Former owner of... (sold through this site)
Dell Mini 9
Other Mods - 2Gb RAM, RunCore "64"Gb SSD, Dell Wireless 1505 b/g/n, Dell Bluetooth, US "Int'l" Keyboard