It takes a bit of practice, but a few months of working at it, learning all the notes on the fingerboard, learning to incorporate the low B string as opposed to thinking of it as a thumb rest until you need to go below low E all are important to making the issue go away in your mind. The reason I say this is because your statement makes it seem like you don’t want a 5 string in your hands on a bandstand unless it’s really needed. One of the biggest pleasures to me about 5 string is I have all the notes on the 4 string above the 5th fret on the 5. For instance, 5th fret B string is the low E, 6th fret is the F you find on your E string at fret 1, 7th fret is the F# you find at fret 2 on the E string- this means that you can have your hand at the middle of the neck and be playing in the full traditional bass range, if you want. Learn to work with the 5 string and learn to think of the B string as useful, and you won’t worry about ‘needing a 5’- you might start wondering if you even want to take a 4. Personally I play 4, 5, and 6 on a bandstand and don’t think twice about it, just have to mentally roadmap what I have in my hands for a few seconds.