I really think that getting a C trumpet is avoiding the issue. Learning to transpose does take a little practice but it's not all that hard. Should come much easier than the conversions involved in civil engineering.
Try starting with reading some familiar songs and play up 1 step. Accidentals may throw you at first, but if you know the melodies you'll recognize immediately when you hit a wrong note. As you get better, try playing songs covering a wider range and in different keys. You'll get it pretty soon!