Your best bet is a site like
www.gunbroker.com - that, or a 'good' gun show.
Don't forget to add things like FFL fees and shipping when you peruse the web sites.
If you do decide on an on-line purchase - look on gunbroker for ultona - Joel seems to get Colts fairly easily, and his prices are very fair - as several folks will attest.
Vaya,
Scouts Out!