Can you say what you are intending to use it for? It can make the world of difference if you are recording single birds a long way away or interested in recording the ambient birdsong you hear in your garden overnight for later identification.
I would always recommend getting a furry windshield for the DR-05, or any recorder for that matter as sooner or later you will need to use the base recorder with its built in mics outdoors and the windshield will help for a cleaner recording.
Most folks who buy an external microphone on this forum, go for the Sennheiser ME66/ K6 combination.
It consists of the ME66 microphone with a K6 powering module that contains a battery to power the microphone as your recorder is not designed to provide that power. There are two versions of the K6 one with and one without the battery, so getting this right one is important. The only other thing you would need is a cable that converts the 3 pin connector on the microphone to the 3.5 mm stereo jack into your recorder. The signal from the microphone is mono, so the cable you need is one that splits the mono signal into two mono signals. Its this cable that is the area where most people come to grief, so its best if you can discuss this with the person you are buying from.
Go to the top screen for this Bird Sounds recording .... part of the Forum and search for ME66 - you will find many threads discussing this.
There are of course other microphones, but this is the most popular.
Have fun
J