Whether over or in the ear, I would start looking at models from the two companies I fared well with regarding headphones, AKG and Sennheiser on Amazon, which sometimes has useful information in customer reviews and comments on these.
Then on the company site for some advertorial info.
Maybe on head-fi.org, a forum specialising in headphones and the gear around them.
I thought that Koss earbuds were okay once, but do not know the model; they were around 50 bucks. The loosely-fitting other in-ear ones are more comfortable for me though.