Layered approach. One is to list for yourself features you must have, features you'd like, features you absolutely want to avoid.
Second is to search yachtworld.com for single-engine diesel boats between 40-50' and under about $325K. This is a preliminary technique only, meant to put boat pictures in front of you... so you can look for brands/models that may seem attractive and have the right features. (Many of those same models will also have twin engine versions, but you can search on that later. The initial single-engine search will usually get you more "trawler-like" returns.)
Third is to look more closely at any other models from the brands that first appeal to you.
Other folks here can name some likely brands, but I'm usually a little brand-agnostic during early investigation. For example, we searched on boats with a flying bridge and STAIRS (not ladders) -- a must have, for us -- and that immediately eliminated lots of brands/models, got subsequent searches down to a much more manageable level.
Once you're into the search process and open up the criteria to include twin engines, you may also find many suitable boats that are not at all trawler-like -- motor yachts and so forth -- but which can be driven much like a trawler at your discretion.
-Chris