I am a new parent and where can I get a good quality baby cot?

Depends where you live but I imagine every baby/new mum kind of shop will sell good quality cribs and cots. What makes a good one? Well, as a parent of two boys is is very simple. The more you pay the better to item, there is a certain give and take but really that's it. It's like buying a car; there are good and bad ones within a price range but in a higher price range the worst car is better than the best from the lower price range.. if you see what I mean. I would not advice shopping online, you need to see and feel the cot/crib before you buy it. You also need to consider other aspects and features, some include changeable mattresses, wood vs plastic, some convert down to beds as the baby grows, some convert into playpens, etc etc...
Baby and "new mum" magazines often have a 2nd hand section as well and that is often a good place to look for stuff. Of course there is always just asking around among friends, family and colleagues, you might be surprised how many people have old baby stuff stored in attics and garages and you might find one going for free that suits your needs. Good luck.